35
Australian Dental Journal, February, 1976 Volume 21, No. 1
Cryosurgerv Mark Jolly
Professor of Oral Medicine and Oral Surgery, University of Sydney
ABsmm-Cryosurgery offers a means of destroying tissue by subjecting it to extreme cold. The mechanisms by which cells die are as yet poorly understood, but reliable and predictable clinical results have been obtained in the treatment of a wide range of benign and premalignant oral lesions. Its effectiveness in the primary treatment of malignant oral lesions has not been adequate1 assessed but at least it offers palliation and relief of intractable pain where conventionar cancer thera y has failed. The use of carbon dioxide ‘snow‘ x8s been tested and found to be a simple and effective means of treating superficial benign lesions of the mouth.
Introduction Some 300 years passed from the time Robert Boyle discovered that freezing could kill cells until the dental profession came to appreciate the therapeutic potential of extreme cold. This is surprising since dentists have earned a reputation for therapeutic inventiveness, innovation and ready adoption of new ideas. Evidence to support this is not difficult to find; perhaps the greatest event in the history of medicine was the discovery by the young American dentist William Morton of the general anaesthetic properties of ether. He gave the first fully documented and attested general anaesthetic on 16th October, 1846 in the Massachusetts General Hospital. After Carl Koller found in 1884 that cocaine had local anaesthetic properties it was quickly seized upon to provide dental anaesthesia and to the present day dentists have played a significant role in
* Literally
Frost-surgery. Greek: kryos = frost.
developing and applying new methods for the control of anxiety and pain. However, the first successful clinical cryosurgery was reported by a dermatologist, A. Campbell Whitel, in 1899. He applied liquid air by cotton-tipped applicators (the ‘swab’ method) and by spray to destroy superficial dermal lesions. Cryosurgery has since been used extensively by dermatologists and has proven valuable in most fields of surgery. The upsurge of interest in cryogenics in recent years, together with significant technological advances in equipment have finally focussed attention on the potential that it offers in the mouth. In 1965 Gage, Koepf, Wehrle, and Emming9, a combined medical and dental group, air; its application in medicine and surgery. Med. Rec.. 56:4. 109-112 (July 22) 1899. 2 Ga e, A. A., Koepf, S., Wehrle. D., and Emmings. F.&yotherapy for cancer of the lip and oral cavity. Cancer, 18:12, 1646-1651 (Dec.) 1965. 1White, A. C.-Liquid
36 reported the successful treatment by local freezing of a small number of benign and malignant lesions of the lip and oral cavity, including squamous cell carcinoma and cylindroma. In 1967 Emmings, Koepf and G a g s reported good results from cryosurgical treatment of a variety of benign lesions of the mouth including leukoplakia and papillary epithelial hyperplasia. Thus began a decade of gradually increasing interest in the possibilities offered by the use of extreme cold in the treatment of oral conditions that hitherto had presented problems for established therapeutic techniques. Effects of freezing on cells The basic aim of cryosurgery is the destruction of tissue by freezing. Since freezing can also be used to preserve cells at very low temperatures it is essential to understand the factors that control these two opposite effects. The treatment of benign lesions such as haemangiomata, papillomatosis and denture hyperplasia, may not require complete destruction of every cell in a given region. However, if freezing is to be used to treat malignant tumours the aim must be 100 per cent cell death. Leibo and his colleagues4 found this very difficult to achieve and after freezing bone marrow cells at various rates, down to -196°C a few colonies were often still viable and able to be cultured, even though the survival rate was 1 per cent or less. In considering the reason why individual cells can survive conditions lethal to their neighbours Farrant6 did not favour a theory of genetic resistance to freezing and thawing damage. Rather, he suggested that it was due to the geometry of the specimen and the cooling procedure, whereby all cells in any one specimen were not uniformly exposed to identical conditions during freezing and thawing. It is obvious that if total cell death is the objective, the destructive factors in the freezing process must be intensified to the maximum and the preserving factors correspondingly minimised. A search of the literature relating to the effects of intense cold on living cells shows the extreme complexity of the many changes that occur during freezing and thawing. When it is remembered
Australian Dental Journal, February, 1976 that the physical changes in the ‘simple’ freezing of water are not yet fully understood, it is not surprising that the corresponding changes in living cells, with their complicated chemical and physical structures, are still very obscure. Nevertheless, if cryotherapy is to be intelligently applied to the mouth we must have some understanding of the various effects it will produce. Therefore in the section that immediately follows, I have attempted to produce a simplified account of the main factors that are thought to damage cells by freezing and thawing. Those who would read more widely are referred to excellent reviews by Merymana, Wolstenholme and O’Connor7 and von Leden and Cahana. Fadom implicated In crydestruction It is accepted that no single factor is responsible for the lethal effect of freezing but a combination of factors, including the following:
Extracellular crystallisation. Jntracellular crystallisation. Concentration of extracellular and intracellular solutes to toxic levels. Mechanical injury by disruption of cell contents, membranes and possibly macromolecules. Dehydration. Denaturation of cellular proteins and protein complexes* and inactivation of enzymes. Thermal shock. Ischaemia and infarction. Cryo-immunisation. The relative effects of these factors appear to be particularly influenced by cooling and thawing rates. Because of the interrelation between several of these factors they will not be discussed as individual and independent phenomena. It should also be noted that there are many conflicting theories and much seemingly conflicting evidence on the influence of each of these factors; thus the following condensation represents the interpretation of one individual.
* Alteration 3Emmings. F . G., Koepf, S. W., and Gage, A . A . - C r y o therapy for benign lesions of the oral cavity. J. Oral Surg.. 25:4. 32G326 (July) 1967. 4 Leibo, S. P., Farrant, I., Mazur, P., Hanna, M. G . , and Stem cell Smith, L. H.-Effects of frecLing on suspensions: interactions of cooling and warming rates in the presence of PVP, sucrose. or glycerol. Cryobiology, 6:4, 315-332 (Ian.-Feb.) 1970. 6 Farrant, J.-Cryobiology: The basis for cryosurgery. In. Cryogenics in surgery. Edits. von Leden H., and Cahan, W. 0 . New York, Medical Examinhion Publishing Co., Inc., 1971 @. 32).
of their chemical or physical properties in such a way as to affect their vital functions.
a Merman, H. T., Edit.-Cryobio!ogy. London, Academic Press, 1966 (€V. 775). I Wolstenholme, G . E. W., and O’Connor. Maeve, Edits.The frozen cell. A Ciba Foundation Symposium. Lon. . don, Churchill, 1970 (pp. 316). 8 v o n Leden, H., and Cahan, W. G., Edits.-Cryogenics in surgery. New York, Medical Examination Publishing Co.. Inc., 1971 @p. 539).
Australian Dental Journal, February, 1976
Extra- and idracellular crystalhtion It is known (but not understood) that slow rates of cooling favour extracellular ice formation and fast rates cause concurrent extra- and intracellular freezing. When crystals form extracellularly, water is removed from these spaces as ice and the remaining extracellular fluid becomes hypertonic, causing water to pass from the cells to maintain intra- and extracellular equilibrium. This dehydration of the cells produces an increase in their electrolyte concentration. If however, the rate of water diffusion from the cells does not keep pace with the rate of extracellular ice formation, then intracellular crystallisation also occurs. Merymano noted that during slow cooling extracellular crystals grew to many times the size of the cells which were thus compressed in a concentrate of their own solutes. On thawing the cells reimbibed their water and under the light microscope appeared undamaged. Mazur and coworkers10 found that rapid freezing was more damaging to mammalian cells than slow freezing and attributed this to iatracellular ice formation. Slow warming was found to be more harmful than rapid warming, presumably because it allowed maximum recrystallisation with formation of large intracellular ice crystals. Levitt and Dearll explained the mechanism of injury primarily as the production of permeable 'holes' in the lipid layer of the plasma membrane by large intracellular crystals; and this concept was supported by electron microscopic examination of frozen cells12. Thus it appears that maximum cell damage is achieved by combining a rapid freeze with a slow thaw.
Concentration of extra- and iatrarellular solutes to toxic levels If cooling is maintained at a slow rate, concentration of both intra- and extracellular solutes occurs and if prolonged the concentration reaches a toxic level. Freezing therefore exposes the cells 9 Meryman
H. 3 &hod. 1 7.
T.-Physical limitations of the rapid freezProc. Roy. Soc. B., 147929, 452459 (Dec.)
lOMuur, P.. Leibo. S. P.. Farrant, J.. Chu, E. H. Y.. Hanna. M. 0.. and Smith, L. H.-Interactions of cooling rate, warming rate and protective additive on the survival of frozen mammalian cells. In, The frmen cell. Wolstenholme, G. E. W and O'Connor. Maeve, Edits. A Ciba Foundation' Symposium. London, Churchill, 1970 (pp. 69-85). 11 Levitt. J.. and Dear. J.-The role of membrane aroteins in f ke& injury and resistance. -In, The fro& cell. Wolstenholme. G. E. W.,and O'Connor. Maeve, Edits. A Ciba Foundation Symposium. London, Churchill.
__
1970 (DD.149-173).
F., Younp, D. E., Arnold, E. A., and ~ ~ ~ R. E.-Effects of freezinn and thawinn on the structure. chemical constitution. a d function of-cytop!asmic struc; tures. Fed. Proc., 24:15, S-1444-168 (March-April)
12 Trump, B.
1965.
37 to an environment of stroog salt solution and thawing then subjects them to weak salt solution producing a cycle that maximises the effects of different intra- and extracellular osmotic pressures13 and deranges the normal chemistry of the cells. In the 'iceball'* that forms during cryosurgery there is a central zone of rapid cooling (near the cold source) where damage is largely physical and a peripheral zone of slow cooling near the warm unfrozen tissue where the lethal effects are caused by chemical changes. However, between them there may be an 'escape zone'" where neither process is sufficiently effective to produce cell death. Mechanical injury At one time it was thought that rapid freezing may cause mechanical injury because of different coefficients of expansion of the various cell component@ but this was later discounted by Merymanu. Nevertheless, some cells can be killed by rapid cooling at temperatures above freezing and dilTerences in thermal expansion may be involved in this phenomenon known as thermal shock.
Dehydration and desaturation of protein camplexes Water plays a critical role in the establishment and maintenance of the spatial relationship of many cellular macromolecules and its removal could be a significant factor in denaturing proteins. Loss of water allows abnormal physical contact between molecules which in turn permits formation of unnatural cross linkages that remain after thawing's, resulting in chemical and physical changes. K l o W proposed that an increase. in concentration of cellular urea also has the ability to disorganise the hydration lattice and thus denature proteins. Freezing and thawing also have been shown18 to reduce the activity of certain enzymes. *The frazcn mass of tissue. J. E.-The hacmolysis of human red bloodcells by freezin and thawing. Biochim. Biophys. Acta.
13 Lovelodr.
1 0 414-426. 1943.
14 Leopard P. J
and Poswillo D. E -Practical cryosurgery for oril lesi&s. Brit. D.J.: 1365; 185-196 (March) 1974. ISMeryman. H. T.-Review of biological freezing. In, Cryobiolopy. Edit. Meryman. H. T. London, Academic Press, 1966 @p. 1-114). 16 Levitt. J.-Winter hardiness in plants. In. Cryobiology. Edit. Meryman. H. T. London, Academic Press, 1966 (Pp. 495-563). 1 of water structure in macromolecules. ~' KlOtz, ~ l I. l M.-Role , Fed. Proc.. 24:15. $244-33 (March-April) 1965. 18 Chilson, 0. P., Costello. L. A,. and Kaplan, N. 0.Effecb of freezing on enzymes. Fed. Proc., 24:15. S-55S-65 (March-April) 1965.
38
Thermal shock Lovelock19 found that red blood cells were lysed by rapid cooling without actually freezing and attributed the damage to differences in thermal expansion of lipid and protein components of the cell membranes. There is no evidence that the mechanism is significant in cryosurgery. Ischaemic infarction “No cell within the cryolesion survives ischaemic infarction, regardless of its sensitivity to cold”20 and vascular stasis may well be the most important factor producing cryonecrosis in the living animaP1. Nevertheless it has been found that the walls of large blood vessels remain intact after freezing and “a return of blood flow will occur on thawing in all but the smallest vessels”22. However, the important factor would be the cessation of nutrient supply at the cellular level. Whittake93 observed that: 1. During and immediately after application of the cryoprobe there was complete stasis in the area. 2. Blood flow was restored within one minute after removal of the probe in the larger arteries, in three minutes in the venules and in ten minutes in the smallest capillaries. 3. Flow continued normally u p to two hours post-operatively and then became sluggish, followed by stasis in the smaller vessels y d by five hours this had spread to all except the larger arterioles. The situation was similar at 24 hours. Electron micrographs of the epithelium showed some cellular damage as early as one minute after cryosurgery and severe damage within one hour. Thus the effect of cryosurgery appears to be twofold - direct cell damage by freezing and secondary effects following vascular stasis about two hours later. Whilst Whittaker described the “restoration of the blood flow within a few minutes of thawing”, it is possibly of significance in the treatment of malignant lesions that frostbite studiesa4-25 have shown marked hyperaemia after thawing and “high pressure” in capillaries with “rapid lymph flow from the injured region”25.
Australian Dental Journal, February, 1976 Cryc+immunisation It has been suggested that tissue damaged by freezing may act as an antigen and provoke an antibody response. Promising results have been reported26 from animal studies but there is no definitive evidence from man, although anti-heart antibodies have been demonstrated in one quarter to one third of a group of patients with myocardial infarction2’ and it is possible that ischaemic infarction produced by freezing may have a similar effect. The hypothesis is attractive and must be investigated but at present its significance must remain open to question. Cryosurgical Equipment The application of cryotherapy to the mouth requires equipment that has the following capabilities:
The cold source (which is really a means of extracting heat-a heat sink) must be small and sufficiently manoeuvrable to reach the various parts of the mouth. It must be controllable to the extent that selected areas can be frozen without damaging nearby structures. It should be able to maintain the required temperature for as long as required. The temperature of the cold source should be variable. The cold source should be fitted with a thermocouple so that the temperature at the tissue surface can be easily read by the surgeon. The rate of thawing should be controllable. Cryosurgical equipment is now available that meets several but not all of these requirements. Most units deliver the refrigerant to the tissues by means of a partially insulated tube (the cryoprobe) and either employ liquid nitrogen or the expansion of a compressed gas for cooling. Those using liquid nitrogen either deliver it to the tissue through a fine nozzle as a direct spray, or CUCUlate it within a ‘closed’ probe. The liquid nitrogen equipment provides a minimum temperature Quintanilla, R . , Krusen, F. H., and Essex, H. E.-Studies on frost-bite with special reference to treatment and the effect on minute blood vessels. Am. J. Physiol., 149:1, 149-161 (April) 1957. 25 Crismon, J. M and Fuhrman, F . A.-Studies on gangrene following cold injury: VI. Capillary blood flow after cold injury, the effects of rapid warming, and sympathetic block. J. Clin. Invest., 26:3. 468475 (May) 1947. 28 Shulman, S . , and Zappi, E.--Cryo-immunology: an aspect of cryobiology. In, Cryogenics in surgery. Edits., von Leden, H., and Cahan, W. G. New York, Medical Examination Publishing Co., Inc., 1971 (pp. 42-79). WEhrenfeld, E. N., Gery, I., and Davies, A. M.-Specific antibodies in heart-disease. Lancet, 1:7187. 1138-1141 (May) 1961. 24
19 Lovelock, J . E.-Physical
instability and thermal shock in red cells. Nature, 173:4406, 659-661 (April) 1954. 20 Gill, W., Long, W., Fraser, J., and Lee, P.--Cryosurgery for neoplasia. Brit. J. Surg., 57:7, 494-502 (July) 1970. 21 Fraser, J. and Gill W.4bservations on ultra-frozen tissue. Brit. 1. Sur;., 54:9, 770-776 (Sept.) 1967. 22 Gill, W., Fraser, J., Da Costa J. and Beazley R.-The cryosurgical lesion. Amer. Suri., 36:7, 437445 (July) 1970. 23 Whittaker. D . K.--Cryosurgery of the oral mucosa: a study of the mechanisms of tissue damage. Dent. Pract., 22:12, 445-451 (Aug.) 1972.
Australian Dental Journal, February, 1976 approximating -195°C. The other type of unit employs the Joule-Thomson principle whereby the rapid expansion of a compressed gas through an orifice causes a profound fall in temperature. The gas (usually nitrous oxide) is delivered through a fine inner tube from which it escapes into the closed end of a larger outer tube-the cryoprobe (Fig. 1). When activated the temperature of the tube tip rapidly falls to the vicinity of -70°C. I use a unit of the latter variety, the Keeler T.C.C. 10 Cryosurgical Unit (Fig. 2). It has a heating coil built into the probe that automatically defrosts the tip and quickly frees it from the frozen tissue when the gas supply is cut off.
Temperature There is no known critical temperature (within the range of clinical feasibility) that can be said to be invariably lethal to animal cells regardless of other factors, the rate at which freezing and thawing take place being of greater significance than the lowest temperature reached by the tissue. Some types of cells have been destroyed at temperatures above freezing point by rapid coolinglo. On the other hand Gye, Begg and Craigiea8 reported the ability of mouse sarcoma to grow and develop fresh tumours after being frozen to -79°C for many months and Sherman28 demonstrated the survival of two types of tumour cells after freezing them to -196°C. However, Hausamen30 stated that the cell killing effect of cold can be attributed exclusively to temperatures between -5°C and -50°C and Lovelock13 demonstrated a critical temperature range of -3°C to 4 0 ° C within which red blood cells were irreversibly damaged. Poswillo31 stated that "virtually all biological tissues subjected to a temperature of -20°C or below for a minute or more undergo cryogenic congelation or necrosis". In attempting to assess the temperature of the boundary of the cryolesion within which infarction will occur Gill and his colleagues20 suggested the critical lethal temperature of living tissue in situ to be -2 & 2°C.
W. E., Beg& A. M., Mann I., and Craigie, J.The survival of activity of mo& sarcoma tissue after freezing and drying. Brit. J. Cancer. 3 2 , 259-267 (June)
18 Gye,
1949.
28 Sherman, J. K.-Survival
of higher animal cells after the formation and dissolution of intracellular ice. Anat. Rcc., 144:3, 171-177 (Nov.)1962. 30 Hausamen, J. E.-The basis, technique and indication for cryosurgcry in tumours of the oral cavity and face. J. max.-fac. Surp., 3:1, 4149 (March) 1975. 31 Poswillo, D. E.-A comparative study of the effects of electrosurgery and cryosurgcry in the management of benign oral lesions. Brit. J. Oral Surg., 9:1, 1-7 (July) 1971.
39 At first sight, the range of temperatures quoted seems bewildering and the data presented by the various researchers seem to conflict. On the one hand some cells are reported to have survived exceedingly low temperatures and on the other
Fig. 1.-Diagrammatic illustration of Kttler cryoprobe. Upper sketch shows details of gas flow. Lower sketch shows the arrangement of the built-in heating and defrosting system.
Fig. 2.-Kedeer
T.C.C. .lo cryosurpery unit with probe on stenlc tray above.
hand some cells are destroyed at temperatures near the freezing point of water. Therefore it must be rememabered that many factors contribute to the death or survival of cells and that the conditions under which the various investigations were carried out doubtless varied considerably. In the present writer's understanding temperatures below -50°C would not be necessary for total cell destruction provided the freeze-thaw cycles were applied with an appreciation of the factors involved in cryo-destruction. Nevertheless there are some advantages in the use of probes operating at lower temperatures. The lower the probe temperature, the more rapid will be the rate of cooling and the larger will be the volume of
40
tissue frozen. Fraser and Gill’s work21 was of considerable practical value and drew attention to the tissue temperature gradient in the vicinity of the cryoprobe. They experimented on the livers of living rats using a probe tip temperature of -190°C applied for four minutes. Temperatures measured in the resultant iceball showed a steep gradient, k i n g -56°C 2 mm from the probe tip, -24°C at 4 mm and -12°C at 8 mm. Nevertheless histological changes were uniform throughout the lesion (which extended beyond the 8 mm radius) and the whole of the cryolesion was destroyed, indicating “a lethal effect at temperatures higher Cell death in the periphery of the than -12°C”. lesion was attributed to ischaemia rather than crystallisation. It is of note that they observed a number of differences between the reaction of normal tissue and that of neoplastic tissue and the zone of destruction appeared less extensive in the latter. Clinical procedure The clinical procedure is deceptively simple, but responsible and successful treatment must be based on accurate assessment of the nature of the lesion and on an understanding of the various parameters of the freezing process. The lesion should be moistened with saline or saliva and the cryoprobe applied to it at room temperature. The instrument is activated (usually by foot-switch) when the probe temperature will drop rapidly and within a few seconds it becomes frozen to the tissue. As the surrounding area freezes it turns white and the perimeter of the iceball formed is quite obvious. The shape of the cryolesion produced is said to be a hemisphere based on the radius of the area frozen at the surface22. If the probe were depressed into the tissue a distance equal to, or greater than the radius of the cryolesion a completely spherical iceball would theoretically be formed. Pressure on a lesion suspected of malignancy is obviously undesirable because of the possibility of dispersal of tumour cells. However there is advantage in exerting some pressure on a highly vascular benign lesion such as haemangioma in order to reduce blood supply (and heat) brought to the area and thus increase the depth and volume of tissue frozen. A local anaesthetic field block containing vasoconstrictor may also be helpful, as is pressure on the artery supplying the area. The depth of freezing can be reduced by gently lifting the probe once it is frozen to the tissue surface. Changing the angular relationship of the probe to the tissue surface once freezing has commenced is to be
Australian Dental Journal, February, 1976 avoided as the tissue attached to the probe will be snapped off leaving a raw, bleeding surface after thawing. This defeats one of the aims of cryosurgery, namely a bloodless field. Gill, Fraser, Da Costa, and Beazley22 demonstrated that maximum surface contact before lowering the probe temperature produces the greatest radius of freezing. They also showed that with the same probe and freezing temperature, repeated freeze-thaw cycles in the same location produced successively larger iceballs and the rate of freezing was correspondingly increased. This phenomenon seems to be due to an increase in thermal conductivity of the previously frozen tissue. In this way the size of the cryolesion can be increased by repeating the freeze-thaw cycle up to a maximum of five to seven times32. The duration of freezing is obviously significant and Gill and colleagues” found that the volume of tissue frozen bears a logarithmic relation to the duration of freezing. The maximum volume frozen by a given probe and temperature required up to two hours to achieve, but 80-90 per cent of the maximum effect was achieved in the first 15 minutes. Even this period is burdensome under clinical conditions and freezing times of one to four minutes are commonly recommended; the only likely disadvantage being the smaller size of the cryolesion produced. As quoted earlier, Poswill0 31 was of the opinion that tissues subjected to -20°C or below for one minute or more would be destroyed. However, in the same paper he warned against the tendency to over-estimate the amount of destruction produced by the cryoprobe and recommended that “all lesions should be treated by freezing for two minutes and thawing and re-freezing to be certain of achieving a satisfactory tissue ‘kill”’. Thawing is fairly rapid in the mouth, taking no more than a minute or SO under natural conditions. However it can be delayed by compression of the arterial supply and by keeping the lesion exposed to the air. If the iceball is allowed to contact nearby vital teeth intense dental pain can be caused. Cryosurgical equipment with variable temperature would permit prolongation of the thawing process.
Pain Pain is not usually a problem with cryosurgcry and many procedures can be carried out without anaesthesia. However, this is not always predictable and some patients request local anaesthesia after the first freeze-thaw cycle; thawing usually causes more discomfort than freezing and the tongue seems more sensitive than other parts of the mouth. The post-operative period is often
Australian Dental Journal, February, 1976 completely painless but the tongue again can be the principal exception and post-operative analgesics may be needed.
Repeated freeze-thaw cycles Gill, Fraser, and Carter32 made a clear distinction between ,the term “multiple freezing” indicating more than one freeze but at daerent sites, and “repetitive freezing” implying repeated applications of the probe at ,the same site. Similar terminology will be used here. As stated earlier there is the possibility of an escape zone within the boundary of a cryolesion in which cells may survive freezing. It has been suggested that this obstacle might be overcome by employing multipletipped probes that would produce overlapping zones of freezing. Whilst such an instrument may have other advantages, the clinical application of the complex geometry of partially overlapping spheres does not appeal to me and there would still seem to be the possibility of parts of each escape zone not being covered by the lethal zones of adjoining spheres. A more reliable way of dealing with the hypothetical escape zone would be to repeat the freeze-thaw cycle in precisely the same area a number of times. In this way the successive iceballs formed will be concentric and the inner lethal zone of each successive iceball should extend to cover the escape zone of the preceding one. Multiple freeze-thaw cycles Lesions too extensive to be covered by the repetitive freezing technique can be treated by multiple or serial freezing. Thus each part of the lesion will be frozen and thawed two or more times until the whole area has been covered. It is especially desirable to ensure that the entire periphery of the lesion has been adequately treated, particularly if it is thought to be malignant. In the latter case every part of the tumour should be exposed t o at least a triple three minute cryo-cycle30 with adequate time allowed for intermediate thawing. Staging rhe Treatment One of the: advantages of cryosurgery is its flexibility. Large benign lesions may be treated in stages, with areas treated and intervals between treatments scaled to meet the needs of the patient. For example. extensive or multiple haemangiomata or lymphangiomata may be divided into convenient regions so that post-operative swelling and interference with normal function after each treat33
Oill, W., Frsse:, J . , and Carter, D. C.-Repeated freezerthaw cycles in cryosurgery. Nature, 2195152, 410-413 (July) 1968.
41
ment can be confined to one area of the mouth. Staging the treatment of malignant lesions may be contra-indicated because of time lost, unless the lesion is inoperable and cannot be managed by any other means.
used to produce carbon dioxide snow/acetone ‘slush’. Arrow ipdicatu chamois leather
Fig. 3.-Equipment
bu.
Carbon dioxide snow The writer has introduced the use of carbon dioxide snow for the treatment of superficial oral mucosal lesions. It is used either in the solid form as a ‘stick’ that has been compressed in a mould, or with the addition of acetone to form a ‘slush’. Both forms provide a temperature in the vicinity of -80°C; the solid form being slightly colder, but the slush offering greater ease of application. To prepare the slush, carbon dioxide is released from a cylinder (Fig. 3) under pressure into a small chamois leather bag where the expanding gas cools rapidly below its freezing point and solidifies. The resultant ‘snow’ is emptied into a small stainless steel dish and acetone added till the consistency is such that it will adhere to the cotton-tipped end of a swab stick. The adherent mass can be shaped by moulding it against the inside of the bowl to give it a spherical, cylindrical, or angular form or whatever shape is convenient for application to the lesion. Anaesthesia is virtually never required for this form of cryotherapy and no special preparation of the mouth is needed. The refrigerant is touched onto the lesion and each area frozen for 5 to 30 seconds depending on the depth of penetration The freeze-thaw cycle is usually required. repeated at least once. The maximum depth of tissue destruction achieved by this method is of the order of two to three mm. The stick of carbon dioxide snow is generally less convenient to use but has the advantage that
42
it can be applied to the tissue with pressure and thus give slightly greater depth of freezing. The swab-stick technique is particularly useful for treating widespread shallow benign lesions, e.g. extensive leukoplakia that has been demonstrated by biopsy to be benign in nature. Two precautions need to be taken in its use. First, even a well-compacted globule on the swab-stick is still quite friable and should be applied without force, otherwise it may break u p and fall into the mouth. Second, when used toward the back of the mouth, there is considerable 'fogging' of the air in the mouth resulting in loss of visibility. nis can be cleared by the use of an ordinary oral aspirator held near the area under treatment.
Australian Dental Journal, February, 1976 Clinical results are in agreement with Poswil10~~ who observed that less scar tissue was produced than by excision and suture.
Cryorurgery in the mouth Excellent evaluations of the effediveness of cryosurgery in the treatment of oral lesions have been published, Poswillo33, Leopard and Poswill0'4. A wide range of benign lesions lend themselves admirably to treatment. However, special mention should be made of a few that have posed therapeutic problems with conventional techniques, but are amenable to treatment by freezing. The outstanding example of the value of this new technique is in the treatment of angiomatous and other very vascular lesions (Fig. 4). Apart Port-operative course from the troublesome haemorrhage during con'The post-operative period is usually uneven,tful. After shallow freezing patients generally report ventional surgery, the recurrence rate after excicomplete absence of post-operative pain. Deep sion is disturbingly high. Each recurrence requires and extensive freezing (particularly of the tongue) the patient to submit to further surgery and poses can resu1,t in moderate to severe discomfort an ever increasing problem for the surgeon to decide where the boundaries of his next surgical requiring analgesics for a few days. idervention will be. Cryosurgery offers a simple Swelling is usually moderate, begins shortly and effective answer to this problem. Small after thawing, reaches a maximum within 24 lesions usually respond to a double freeze-thaw hours, and requires no special treatment. The cycle and extensive lesions can be treated in exceptions, in my experience, are very vascular appropriate stages (Fig. 5). Recurrences can still lesions and lymphangiomas. These have been occur but pose no problem for re-freezing with observed to swell markedly within minutes of little inconvenience 'to the patient (Fig. 6). Patients treatment (? reactive hyperaemia plus damage to with widespread oral haemorrhagic telangiectasia thin-walled vessels) and to reach impressive pro- who are inconvenienced by repeated bleeding have portions within 24 hours. usually had the troublesome lesions excised or Caution should be observed when freezing areas cauterized and it is alarming to note that some where swelling could interfere with the airway have received repeated radiotherapy for this cone.g. base of tongue, floor of mouth and tonsillar dition. As this is an on-going problem increasing area. In these cases treatment may be staged or with age, the ease and convenience of treatment if this is contra-indicated the patient should be with cryosurgery is a boon to them (Fig. 7). admitted to hospital for treatment and post- Multiple pregnancy tumours offer a further operative observation. example of vascular lesions with a high recurrence With ordinary post-operative care, infection of ra,te that lend themselves to cryotherapy. the cryolesion is rare and is seen less frequen,tly Papillomatosis of the palate is a lesion that has than after conventional surgery. Post-operative provided therapeutic problems for both patient haemorrhage is exceedingly rare; however it must and surgeon. Conventional surgical excision is be recognised as a possible sequel to infection. technically difficult, dermabrasion is bloody and When examined two to three days after surgery lacking in finesse, and electrocautery is malodourthe cryolesion is usually covered by a yellow-grey ous and disturbing for the patient. All these slough and its margins are demarcated from the procedures also result in considerable postsurrounding tissue. There is surprisingly little operative pain. Cryosurgery offers a simple techinflammatory reaction to be seen in the adjacent nique, a bloodless field and little post-operative tissue. Irrigations with dilute hydrogen peroxide discomfort. and other antiseptic mouthwashes help to remove The third type of lesion that merits special sloughing tissue and keep ,the mouth in a pleasant mention is widespread leukoplakia of ,the oral state. Epithelialisation of soft tissue wounds takes from as little as 10 days up to seven weeks, depending on the size of the area treated. In 33 Poswillo, D. E.-Cryosurgery in and around the oral cavity. I n , Recent advances in surgery. Edit. Taylor S. general, scarring is minimal following cryosurgery. London, Churchill-Livingstone, 1973 (pp. 69-101).
Australian Dental Journal, February, 1976 cavity that is too extensive for removal by conventional surgery or in areas that do not lend themselves to excision (Fig. 8). Electro-surgery is to be avoided because of the subsequent warring and the high incidence of recurrence of the
43
spread shallow lesions. The use of carbon dioxide/ acetone slush has proved simple and effective for the removal of superficial leukoplakia. Recurrence is rare (except when the aetiological factor e.g. smoking, has not been eliminated) and there
Fig. 4 . 4 4 Two haemangiomas right ride of tongue partly thawed after freaing. (b) Sama area four weeks after cryosurgery.
Fig. 5 . 4 . ) One area in the mouth of a young patient with lymphanpiomas in several locations. (b) Same region showing well demarcated sloughing area. (c) Same region almost healed. four weeks after cryosurgery.
original lesion. All leukoplakia of the mouth must first be carefully evaluated and its true nature determined (usually by biopsy). If the lesion does not then respond to conservative treatment the least that should be done is to keep the lesion(.$ under long-term surveillance. However cryosurgery now permits the removal of such wide-
is no discernible scarring. Biopsy can be carried out at any time and can be done whilst the tissues are partially frozen. Apart from the treatment of proliferative lesions, cryosurgery has some place in the trea,tment of ulcerative and erosive lesions. Erosive lichen planus is not characterised by pain except
44
Australian Dental Journal, February, 1976
Fig. 6 . 4 a ) Haemangioma, tip of tongue. (b) Same area with partial recurrence right side four weeks after cryosurgery. (c) Same area, healed and free of haemangioma, three weeks later.
Fig. 7 . 4 6 Patient with. haemorrhagic telangiectasia. The lesion in the centre of the tongue bothered the patient because of spontaneous bleeding. (b) The lesion during thawing. (c) Same area three weeks after cryosurgery.
Australian Dental Journal, February, 1976 when secondarily infected, usually by candida albicans. Nevertheless the lesions cause discomfort and should not be permitted to continue indefinitely because of possible malignant transformation. Personal experience has shown cryo-
45
usefulness in certain circumstances. In 1%5 Gage, Koepf, Wehrle, and Emmingsz reported the successful treatment of malignancy in the mouths of four specially selected patients who had lesions resistant to radiotherapy, lesions in areas not
Fig. 8 . 4 8 ) One of many patch- of leukoplakia in unusual locations in the one mouth and not particularly amenable to surgical excision. (b) Same area free of leukoplakia three wceks after treatment with COnIacetone.
surgical treatment of these erosions to be reasonably successful. Many heal with new healthy epithelium advancing across the lesions some two to three weeks after treatment. On the other hand, it has been disappointing to see recurrence of erosions in some of the areas treated. The anatomical locations of some lesions present problems for conventional surgery and electrosurgery but are amenable to a cryosurgical approach. Lesions involving the free marginal gingivae, or vermilion border of the lip can USUally be eliminated without loss of contour and natural colour. Conventional excision of lesions in the buccal or lingual sulci often results in loss of valuable depth. On the other hand, cryodestruction usually causes little or no loss of sulcus depth. Premalignant lesions that have progressed to the stage of epithelial dysplasia and that are too extensive for conventional surgical excision can be adequately treated with cryosurgery. The use of carbon dioxide snow may not give sufficient depth of freezing and use of a cryosurgical probe is indicated. All parts of the lesion should be subjeuted to two or three freezes of two minutes each with adequate intervals for thawing. Poswill# reported the recurrence of dyskeratotic lesions following electrosurgery and favours the use of cryosurgery.
Mnllsp.nt oral lesions writer has not used CryOsUrgery for the treatment of malignant lesions but recognises its
amenable to excision without disabling surgery, or severe cardiac disease. Gage and KoepP4 later reported on a much larger group of patients and concluded that the results were comparable with whet might have been expected of excision. The main advantages were that the technique was especially suitable for poor risk patients and mutilating operations were avoided. Cherry% obtained excellent short-term results with cryotherapy for four patients with oral carcinoma in whom the prognosis was extremely poor, yet he gave only guarded commendation of the technique. Poswillo33 found cryosurgery of considerable value in the palliative treatment of recurrent oral cancer, in the treatment of metastatic nodes adherent to major vessels and nerves and in attempts to treat large inoperable lesions. He was particularly impressed by its effectiveness in controlling intractable pain. Poswillo also appears to give some credence to the theory that immune response is invoked or at least enhanced by cryodestruction of tumour tissue and quoted Neel, Ketcham and Hammond36 whose work on transplanted tumours in animals demonstrated that in
34Gw, A. A.. and Koepf, S. W.-Cryotherapy as primary treatment for oral cancer. J. Cryosurg., 1: 177-183, 1966. 35 Cherry, J.-Cryosurgery of oral cancer. Arch. Otolaryng., 91:6, 548-551 (June) 1970.
€B.. I. Ketcham, A. s., and Harnrnond. W. 0.Requisites for SuCCeSSful cry0 nic surgery of cancer. Arch. Sbrg., 102:1, 4548 (Jan.$1971.
36N-1,
46 situ tumour destruction by freezing provides greater immunity to subsequent tumour challenge than does tumour removal by excision”. In summary then, it seems that whilst cryosurgery does not replace conventional methods of treatment for oral malignancy, the technique has proven value and possibly unassessed potential. At least it offers hope for poor risk patients and those with lesions beyond the range of surgery or radiotherapy. When dealing with excisable or radiosensitive lesions the disadvantages of cryosurgery must be considered. These include the difficulty of accurately assessing the margins of cryodestruction in three dimensions and the lack of a complete surgical specimen for histological examination.
Discussion Cryosurgery is a form of treatment that enables local destruction of tissue by simple means. There can be n o question of its superiority over conventional methods of surgery for the treatment of certain benign and premalignant oral lesions. The prime examples are angiomatous lesions, palatal papillary hyperplasia and widespread leukoplakia (with or without epithelial dysplasia). In the field of oral malignancy, cryosurgery has largely been used after other forms of treatment have failed or where the patient or the tumour have not been considered suitable for conventional therapy. Numerous successes have been reported and at least it offers palliation and relief of pain. Apart from the ischaemic infarction produced by freezing tissues, the methods by which cells are destroyed by intense cold are complex and as yet poorly understood. There is agreement that many potentially destructive processes contribute to cell death but as yet the relative contribution of each process has not been evaluated. The most disturbing aspect of our current lack of knowledge is that it has not been possible to establish firm criteria that will ensure the certain destruction of all cells in a given zone. On the one hand several eminent authorities have suggested that under cryosurgical conditions (rapid freeze-slow thaw) all cells cooled to the vicinity of -20°C will die; on the other, it is disconcerting t o find good experimental evidence36 that under similar conditions, effective tumour control required repetitive freezing of tissues to temperatures below -60°C. When it is also borne in mind that the temperature gradient in tissue adjacent to the probe tip is extremely steep21 (e.g. -190°C at probe tip and only -56°C 2 mm away) it becomes obvious that
Australian Dental Journal, February, 1976 improved equipment, and extremely low temperatures will be needed before cryosurgery can be confidently used for the primary treatment of oral cancer. Another disadvantage of cryosurgery in the treatment of malignant lesions is the lack of a postsurgical specimen for histological examination. It is true that in conventional cold knife excision the surgeon still has to estimate the boundaries of the lesion, but the entire specimen is available post-operatively when these boundaries can be examined histologically. It has also been claimed by numerous authors that the extent of the cryolesion is predictable and reproducible, but in my estimation nothing could be further from the truth. It may well be that under experimental conditions, predictable and reproducible cryolesions can be produced in one animal after another. However, a great deal more clinical experience is required in the treatment of oral lesions, ideally with probe-thermocouple monitoring of tissue temperatures at known distances below and lateral to the probe tip. A vast amount of such data will be necessary for the various parts of the mouth and taking into account all other variables, before accurately predictable cryolesions can be anticipated. The advantages of cryosurgery are many. Preparation of the patient and the mouth are minimal and equipment and techniques are simple. It has minimal phychological effect upon the patient and does not raise the fears associated with other forms of surgery. Operating times are short and can be scaled to the needs of the patient. Because it produces so little mental and physical stress, it is well suited to the poor risk patient. It offers tissue destruction without haemorrhage and with little operative or post-operative discomfort. Postoperative infection and other complications are rare and scar tissue formation is minimal and usually soft in nature. When the vermilion border of the lip is involved in the cryolesion there is usually restoration of form and normal colour after healing. The possibility that freezing of tumour tissue may change it in such a way (physically or chemically) that it will act as an auto-antigen and provide or intensify an antibody reaction is exceedingly attractive. Whilst there is very limited evidence to support this concept at present, it must command the attenion of all who work in the field of immunology. There is already acceptance of the concept that if ways can be found to induce the body to recognise tumour tissue as ‘non-self‘ and produce antibodies to its own tumour tissue, this would provide the ultimate in cancer therapy.
47
Australian Dental Journal, February, 1976 1.t may well be that some means will be found to intensify the antigenic stimulus of freezing. One of the advantages ascribed to cryodestruction of a lesion is that it ‘fixes’ cells within the iceball thus preventing dissemination of tumour cells during surgery. This is almost certainly a valid attribute of the technique, but it is possible that the immediate post-thawing hyperaemia2c could be intense enough to disseminate tumour cells, particularly in lesions large enough to require repetitive freezing. If this were so, preoperative field block of the area with anaesthetic containing adrenaline may minimise the reactive hyperaemia. Carbon dioxide snow has been used with obvious success for many years in the field of dermatology for the treatment of superficial lesions, notably solar keratoses. The writer has used similar techniques for the treatment of widespread shallow oral lesions. The prime example is widespread leukoplakia that has been investigated by biopsy and found to be innocent in nature. Anaesthesia has not been necessary, postoperative discomfort is virtually nil and results have been gratifying. Its virtues are simplicity
and ease of application and the short clinical time involved in its application. There is no discernible scarring following its use and the usual result is restoration of normal, healthyappearing mucosa.
Condualon Cryosurgery adds a comparatively new therapeutic technique to the repertoire of the dental and oral surgeon. It does not replace conventional methods of treatment except for a small number of special lesions. However it has an unquestionable contribution to make in the treatment of a wide range of benign and premalignant lesions and in the management of malignant lesions in highly selected patients, 1.t should be used with discretion however and where the nature of the lesion is in doubt it should be left in the hands of the appropriate specialist. Department of Oral Medicine and Oral Surgery, University of Sydney, 2 Chalmers Street, Surry Hills, N.S.W.2010
Malnutrition National mortality statistics rarely mention undernutrition as a cause of death. The Inter-American Investigation of Mortality in Childhood, conducted in 18 widely dif€ering areas of the Americas and sponsored by the Pan American Health Organization, indicated that malnutrition was the underlying cause of death in children under 5 years in 7% of cases and an associated cause in 46.2% of cases.-W.H.O. Geneva, VoZ. 29, October, 1975.
Australian Dental Journal, February, 1976 Volume 21, No. 1
Cryosurgerv Mark Jolly
Professor of Oral Medicine and Oral Surgery, University of Sydney
ABsmm-Cryosurgery offers a means of destroying tissue by subjecting it to extreme cold. The mechanisms by which cells die are as yet poorly understood, but reliable and predictable clinical results have been obtained in the treatment of a wide range of benign and premalignant oral lesions. Its effectiveness in the primary treatment of malignant oral lesions has not been adequate1 assessed but at least it offers palliation and relief of intractable pain where conventionar cancer thera y has failed. The use of carbon dioxide ‘snow‘ x8s been tested and found to be a simple and effective means of treating superficial benign lesions of the mouth.
Introduction Some 300 years passed from the time Robert Boyle discovered that freezing could kill cells until the dental profession came to appreciate the therapeutic potential of extreme cold. This is surprising since dentists have earned a reputation for therapeutic inventiveness, innovation and ready adoption of new ideas. Evidence to support this is not difficult to find; perhaps the greatest event in the history of medicine was the discovery by the young American dentist William Morton of the general anaesthetic properties of ether. He gave the first fully documented and attested general anaesthetic on 16th October, 1846 in the Massachusetts General Hospital. After Carl Koller found in 1884 that cocaine had local anaesthetic properties it was quickly seized upon to provide dental anaesthesia and to the present day dentists have played a significant role in
* Literally
Frost-surgery. Greek: kryos = frost.
developing and applying new methods for the control of anxiety and pain. However, the first successful clinical cryosurgery was reported by a dermatologist, A. Campbell Whitel, in 1899. He applied liquid air by cotton-tipped applicators (the ‘swab’ method) and by spray to destroy superficial dermal lesions. Cryosurgery has since been used extensively by dermatologists and has proven valuable in most fields of surgery. The upsurge of interest in cryogenics in recent years, together with significant technological advances in equipment have finally focussed attention on the potential that it offers in the mouth. In 1965 Gage, Koepf, Wehrle, and Emming9, a combined medical and dental group, air; its application in medicine and surgery. Med. Rec.. 56:4. 109-112 (July 22) 1899. 2 Ga e, A. A., Koepf, S., Wehrle. D., and Emmings. F.&yotherapy for cancer of the lip and oral cavity. Cancer, 18:12, 1646-1651 (Dec.) 1965. 1White, A. C.-Liquid
36 reported the successful treatment by local freezing of a small number of benign and malignant lesions of the lip and oral cavity, including squamous cell carcinoma and cylindroma. In 1967 Emmings, Koepf and G a g s reported good results from cryosurgical treatment of a variety of benign lesions of the mouth including leukoplakia and papillary epithelial hyperplasia. Thus began a decade of gradually increasing interest in the possibilities offered by the use of extreme cold in the treatment of oral conditions that hitherto had presented problems for established therapeutic techniques. Effects of freezing on cells The basic aim of cryosurgery is the destruction of tissue by freezing. Since freezing can also be used to preserve cells at very low temperatures it is essential to understand the factors that control these two opposite effects. The treatment of benign lesions such as haemangiomata, papillomatosis and denture hyperplasia, may not require complete destruction of every cell in a given region. However, if freezing is to be used to treat malignant tumours the aim must be 100 per cent cell death. Leibo and his colleagues4 found this very difficult to achieve and after freezing bone marrow cells at various rates, down to -196°C a few colonies were often still viable and able to be cultured, even though the survival rate was 1 per cent or less. In considering the reason why individual cells can survive conditions lethal to their neighbours Farrant6 did not favour a theory of genetic resistance to freezing and thawing damage. Rather, he suggested that it was due to the geometry of the specimen and the cooling procedure, whereby all cells in any one specimen were not uniformly exposed to identical conditions during freezing and thawing. It is obvious that if total cell death is the objective, the destructive factors in the freezing process must be intensified to the maximum and the preserving factors correspondingly minimised. A search of the literature relating to the effects of intense cold on living cells shows the extreme complexity of the many changes that occur during freezing and thawing. When it is remembered
Australian Dental Journal, February, 1976 that the physical changes in the ‘simple’ freezing of water are not yet fully understood, it is not surprising that the corresponding changes in living cells, with their complicated chemical and physical structures, are still very obscure. Nevertheless, if cryotherapy is to be intelligently applied to the mouth we must have some understanding of the various effects it will produce. Therefore in the section that immediately follows, I have attempted to produce a simplified account of the main factors that are thought to damage cells by freezing and thawing. Those who would read more widely are referred to excellent reviews by Merymana, Wolstenholme and O’Connor7 and von Leden and Cahana. Fadom implicated In crydestruction It is accepted that no single factor is responsible for the lethal effect of freezing but a combination of factors, including the following:
Extracellular crystallisation. Jntracellular crystallisation. Concentration of extracellular and intracellular solutes to toxic levels. Mechanical injury by disruption of cell contents, membranes and possibly macromolecules. Dehydration. Denaturation of cellular proteins and protein complexes* and inactivation of enzymes. Thermal shock. Ischaemia and infarction. Cryo-immunisation. The relative effects of these factors appear to be particularly influenced by cooling and thawing rates. Because of the interrelation between several of these factors they will not be discussed as individual and independent phenomena. It should also be noted that there are many conflicting theories and much seemingly conflicting evidence on the influence of each of these factors; thus the following condensation represents the interpretation of one individual.
* Alteration 3Emmings. F . G., Koepf, S. W., and Gage, A . A . - C r y o therapy for benign lesions of the oral cavity. J. Oral Surg.. 25:4. 32G326 (July) 1967. 4 Leibo, S. P., Farrant, I., Mazur, P., Hanna, M. G . , and Stem cell Smith, L. H.-Effects of frecLing on suspensions: interactions of cooling and warming rates in the presence of PVP, sucrose. or glycerol. Cryobiology, 6:4, 315-332 (Ian.-Feb.) 1970. 6 Farrant, J.-Cryobiology: The basis for cryosurgery. In. Cryogenics in surgery. Edits. von Leden H., and Cahan, W. 0 . New York, Medical Examinhion Publishing Co., Inc., 1971 @. 32).
of their chemical or physical properties in such a way as to affect their vital functions.
a Merman, H. T., Edit.-Cryobio!ogy. London, Academic Press, 1966 (€V. 775). I Wolstenholme, G . E. W., and O’Connor. Maeve, Edits.The frozen cell. A Ciba Foundation Symposium. Lon. . don, Churchill, 1970 (pp. 316). 8 v o n Leden, H., and Cahan, W. G., Edits.-Cryogenics in surgery. New York, Medical Examination Publishing Co.. Inc., 1971 @p. 539).
Australian Dental Journal, February, 1976
Extra- and idracellular crystalhtion It is known (but not understood) that slow rates of cooling favour extracellular ice formation and fast rates cause concurrent extra- and intracellular freezing. When crystals form extracellularly, water is removed from these spaces as ice and the remaining extracellular fluid becomes hypertonic, causing water to pass from the cells to maintain intra- and extracellular equilibrium. This dehydration of the cells produces an increase in their electrolyte concentration. If however, the rate of water diffusion from the cells does not keep pace with the rate of extracellular ice formation, then intracellular crystallisation also occurs. Merymano noted that during slow cooling extracellular crystals grew to many times the size of the cells which were thus compressed in a concentrate of their own solutes. On thawing the cells reimbibed their water and under the light microscope appeared undamaged. Mazur and coworkers10 found that rapid freezing was more damaging to mammalian cells than slow freezing and attributed this to iatracellular ice formation. Slow warming was found to be more harmful than rapid warming, presumably because it allowed maximum recrystallisation with formation of large intracellular ice crystals. Levitt and Dearll explained the mechanism of injury primarily as the production of permeable 'holes' in the lipid layer of the plasma membrane by large intracellular crystals; and this concept was supported by electron microscopic examination of frozen cells12. Thus it appears that maximum cell damage is achieved by combining a rapid freeze with a slow thaw.
Concentration of extra- and iatrarellular solutes to toxic levels If cooling is maintained at a slow rate, concentration of both intra- and extracellular solutes occurs and if prolonged the concentration reaches a toxic level. Freezing therefore exposes the cells 9 Meryman
H. 3 &hod. 1 7.
T.-Physical limitations of the rapid freezProc. Roy. Soc. B., 147929, 452459 (Dec.)
lOMuur, P.. Leibo. S. P.. Farrant, J.. Chu, E. H. Y.. Hanna. M. 0.. and Smith, L. H.-Interactions of cooling rate, warming rate and protective additive on the survival of frozen mammalian cells. In, The frmen cell. Wolstenholme, G. E. W and O'Connor. Maeve, Edits. A Ciba Foundation' Symposium. London, Churchill, 1970 (pp. 69-85). 11 Levitt. J.. and Dear. J.-The role of membrane aroteins in f ke& injury and resistance. -In, The fro& cell. Wolstenholme. G. E. W.,and O'Connor. Maeve, Edits. A Ciba Foundation Symposium. London, Churchill.
__
1970 (DD.149-173).
F., Younp, D. E., Arnold, E. A., and ~ ~ ~ R. E.-Effects of freezinn and thawinn on the structure. chemical constitution. a d function of-cytop!asmic struc; tures. Fed. Proc., 24:15, S-1444-168 (March-April)
12 Trump, B.
1965.
37 to an environment of stroog salt solution and thawing then subjects them to weak salt solution producing a cycle that maximises the effects of different intra- and extracellular osmotic pressures13 and deranges the normal chemistry of the cells. In the 'iceball'* that forms during cryosurgery there is a central zone of rapid cooling (near the cold source) where damage is largely physical and a peripheral zone of slow cooling near the warm unfrozen tissue where the lethal effects are caused by chemical changes. However, between them there may be an 'escape zone'" where neither process is sufficiently effective to produce cell death. Mechanical injury At one time it was thought that rapid freezing may cause mechanical injury because of different coefficients of expansion of the various cell component@ but this was later discounted by Merymanu. Nevertheless, some cells can be killed by rapid cooling at temperatures above freezing and dilTerences in thermal expansion may be involved in this phenomenon known as thermal shock.
Dehydration and desaturation of protein camplexes Water plays a critical role in the establishment and maintenance of the spatial relationship of many cellular macromolecules and its removal could be a significant factor in denaturing proteins. Loss of water allows abnormal physical contact between molecules which in turn permits formation of unnatural cross linkages that remain after thawing's, resulting in chemical and physical changes. K l o W proposed that an increase. in concentration of cellular urea also has the ability to disorganise the hydration lattice and thus denature proteins. Freezing and thawing also have been shown18 to reduce the activity of certain enzymes. *The frazcn mass of tissue. J. E.-The hacmolysis of human red bloodcells by freezin and thawing. Biochim. Biophys. Acta.
13 Lovelodr.
1 0 414-426. 1943.
14 Leopard P. J
and Poswillo D. E -Practical cryosurgery for oril lesi&s. Brit. D.J.: 1365; 185-196 (March) 1974. ISMeryman. H. T.-Review of biological freezing. In, Cryobiolopy. Edit. Meryman. H. T. London, Academic Press, 1966 @p. 1-114). 16 Levitt. J.-Winter hardiness in plants. In. Cryobiology. Edit. Meryman. H. T. London, Academic Press, 1966 (Pp. 495-563). 1 of water structure in macromolecules. ~' KlOtz, ~ l I. l M.-Role , Fed. Proc.. 24:15. $244-33 (March-April) 1965. 18 Chilson, 0. P., Costello. L. A,. and Kaplan, N. 0.Effecb of freezing on enzymes. Fed. Proc., 24:15. S-55S-65 (March-April) 1965.
38
Thermal shock Lovelock19 found that red blood cells were lysed by rapid cooling without actually freezing and attributed the damage to differences in thermal expansion of lipid and protein components of the cell membranes. There is no evidence that the mechanism is significant in cryosurgery. Ischaemic infarction “No cell within the cryolesion survives ischaemic infarction, regardless of its sensitivity to cold”20 and vascular stasis may well be the most important factor producing cryonecrosis in the living animaP1. Nevertheless it has been found that the walls of large blood vessels remain intact after freezing and “a return of blood flow will occur on thawing in all but the smallest vessels”22. However, the important factor would be the cessation of nutrient supply at the cellular level. Whittake93 observed that: 1. During and immediately after application of the cryoprobe there was complete stasis in the area. 2. Blood flow was restored within one minute after removal of the probe in the larger arteries, in three minutes in the venules and in ten minutes in the smallest capillaries. 3. Flow continued normally u p to two hours post-operatively and then became sluggish, followed by stasis in the smaller vessels y d by five hours this had spread to all except the larger arterioles. The situation was similar at 24 hours. Electron micrographs of the epithelium showed some cellular damage as early as one minute after cryosurgery and severe damage within one hour. Thus the effect of cryosurgery appears to be twofold - direct cell damage by freezing and secondary effects following vascular stasis about two hours later. Whilst Whittaker described the “restoration of the blood flow within a few minutes of thawing”, it is possibly of significance in the treatment of malignant lesions that frostbite studiesa4-25 have shown marked hyperaemia after thawing and “high pressure” in capillaries with “rapid lymph flow from the injured region”25.
Australian Dental Journal, February, 1976 Cryc+immunisation It has been suggested that tissue damaged by freezing may act as an antigen and provoke an antibody response. Promising results have been reported26 from animal studies but there is no definitive evidence from man, although anti-heart antibodies have been demonstrated in one quarter to one third of a group of patients with myocardial infarction2’ and it is possible that ischaemic infarction produced by freezing may have a similar effect. The hypothesis is attractive and must be investigated but at present its significance must remain open to question. Cryosurgical Equipment The application of cryotherapy to the mouth requires equipment that has the following capabilities:
The cold source (which is really a means of extracting heat-a heat sink) must be small and sufficiently manoeuvrable to reach the various parts of the mouth. It must be controllable to the extent that selected areas can be frozen without damaging nearby structures. It should be able to maintain the required temperature for as long as required. The temperature of the cold source should be variable. The cold source should be fitted with a thermocouple so that the temperature at the tissue surface can be easily read by the surgeon. The rate of thawing should be controllable. Cryosurgical equipment is now available that meets several but not all of these requirements. Most units deliver the refrigerant to the tissues by means of a partially insulated tube (the cryoprobe) and either employ liquid nitrogen or the expansion of a compressed gas for cooling. Those using liquid nitrogen either deliver it to the tissue through a fine nozzle as a direct spray, or CUCUlate it within a ‘closed’ probe. The liquid nitrogen equipment provides a minimum temperature Quintanilla, R . , Krusen, F. H., and Essex, H. E.-Studies on frost-bite with special reference to treatment and the effect on minute blood vessels. Am. J. Physiol., 149:1, 149-161 (April) 1957. 25 Crismon, J. M and Fuhrman, F . A.-Studies on gangrene following cold injury: VI. Capillary blood flow after cold injury, the effects of rapid warming, and sympathetic block. J. Clin. Invest., 26:3. 468475 (May) 1947. 28 Shulman, S . , and Zappi, E.--Cryo-immunology: an aspect of cryobiology. In, Cryogenics in surgery. Edits., von Leden, H., and Cahan, W. G. New York, Medical Examination Publishing Co., Inc., 1971 (pp. 42-79). WEhrenfeld, E. N., Gery, I., and Davies, A. M.-Specific antibodies in heart-disease. Lancet, 1:7187. 1138-1141 (May) 1961. 24
19 Lovelock, J . E.-Physical
instability and thermal shock in red cells. Nature, 173:4406, 659-661 (April) 1954. 20 Gill, W., Long, W., Fraser, J., and Lee, P.--Cryosurgery for neoplasia. Brit. J. Surg., 57:7, 494-502 (July) 1970. 21 Fraser, J. and Gill W.4bservations on ultra-frozen tissue. Brit. 1. Sur;., 54:9, 770-776 (Sept.) 1967. 22 Gill, W., Fraser, J., Da Costa J. and Beazley R.-The cryosurgical lesion. Amer. Suri., 36:7, 437445 (July) 1970. 23 Whittaker. D . K.--Cryosurgery of the oral mucosa: a study of the mechanisms of tissue damage. Dent. Pract., 22:12, 445-451 (Aug.) 1972.
Australian Dental Journal, February, 1976 approximating -195°C. The other type of unit employs the Joule-Thomson principle whereby the rapid expansion of a compressed gas through an orifice causes a profound fall in temperature. The gas (usually nitrous oxide) is delivered through a fine inner tube from which it escapes into the closed end of a larger outer tube-the cryoprobe (Fig. 1). When activated the temperature of the tube tip rapidly falls to the vicinity of -70°C. I use a unit of the latter variety, the Keeler T.C.C. 10 Cryosurgical Unit (Fig. 2). It has a heating coil built into the probe that automatically defrosts the tip and quickly frees it from the frozen tissue when the gas supply is cut off.
Temperature There is no known critical temperature (within the range of clinical feasibility) that can be said to be invariably lethal to animal cells regardless of other factors, the rate at which freezing and thawing take place being of greater significance than the lowest temperature reached by the tissue. Some types of cells have been destroyed at temperatures above freezing point by rapid coolinglo. On the other hand Gye, Begg and Craigiea8 reported the ability of mouse sarcoma to grow and develop fresh tumours after being frozen to -79°C for many months and Sherman28 demonstrated the survival of two types of tumour cells after freezing them to -196°C. However, Hausamen30 stated that the cell killing effect of cold can be attributed exclusively to temperatures between -5°C and -50°C and Lovelock13 demonstrated a critical temperature range of -3°C to 4 0 ° C within which red blood cells were irreversibly damaged. Poswillo31 stated that "virtually all biological tissues subjected to a temperature of -20°C or below for a minute or more undergo cryogenic congelation or necrosis". In attempting to assess the temperature of the boundary of the cryolesion within which infarction will occur Gill and his colleagues20 suggested the critical lethal temperature of living tissue in situ to be -2 & 2°C.
W. E., Beg& A. M., Mann I., and Craigie, J.The survival of activity of mo& sarcoma tissue after freezing and drying. Brit. J. Cancer. 3 2 , 259-267 (June)
18 Gye,
1949.
28 Sherman, J. K.-Survival
of higher animal cells after the formation and dissolution of intracellular ice. Anat. Rcc., 144:3, 171-177 (Nov.)1962. 30 Hausamen, J. E.-The basis, technique and indication for cryosurgcry in tumours of the oral cavity and face. J. max.-fac. Surp., 3:1, 4149 (March) 1975. 31 Poswillo, D. E.-A comparative study of the effects of electrosurgery and cryosurgcry in the management of benign oral lesions. Brit. J. Oral Surg., 9:1, 1-7 (July) 1971.
39 At first sight, the range of temperatures quoted seems bewildering and the data presented by the various researchers seem to conflict. On the one hand some cells are reported to have survived exceedingly low temperatures and on the other
Fig. 1.-Diagrammatic illustration of Kttler cryoprobe. Upper sketch shows details of gas flow. Lower sketch shows the arrangement of the built-in heating and defrosting system.
Fig. 2.-Kedeer
T.C.C. .lo cryosurpery unit with probe on stenlc tray above.
hand some cells are destroyed at temperatures near the freezing point of water. Therefore it must be rememabered that many factors contribute to the death or survival of cells and that the conditions under which the various investigations were carried out doubtless varied considerably. In the present writer's understanding temperatures below -50°C would not be necessary for total cell destruction provided the freeze-thaw cycles were applied with an appreciation of the factors involved in cryo-destruction. Nevertheless there are some advantages in the use of probes operating at lower temperatures. The lower the probe temperature, the more rapid will be the rate of cooling and the larger will be the volume of
40
tissue frozen. Fraser and Gill’s work21 was of considerable practical value and drew attention to the tissue temperature gradient in the vicinity of the cryoprobe. They experimented on the livers of living rats using a probe tip temperature of -190°C applied for four minutes. Temperatures measured in the resultant iceball showed a steep gradient, k i n g -56°C 2 mm from the probe tip, -24°C at 4 mm and -12°C at 8 mm. Nevertheless histological changes were uniform throughout the lesion (which extended beyond the 8 mm radius) and the whole of the cryolesion was destroyed, indicating “a lethal effect at temperatures higher Cell death in the periphery of the than -12°C”. lesion was attributed to ischaemia rather than crystallisation. It is of note that they observed a number of differences between the reaction of normal tissue and that of neoplastic tissue and the zone of destruction appeared less extensive in the latter. Clinical procedure The clinical procedure is deceptively simple, but responsible and successful treatment must be based on accurate assessment of the nature of the lesion and on an understanding of the various parameters of the freezing process. The lesion should be moistened with saline or saliva and the cryoprobe applied to it at room temperature. The instrument is activated (usually by foot-switch) when the probe temperature will drop rapidly and within a few seconds it becomes frozen to the tissue. As the surrounding area freezes it turns white and the perimeter of the iceball formed is quite obvious. The shape of the cryolesion produced is said to be a hemisphere based on the radius of the area frozen at the surface22. If the probe were depressed into the tissue a distance equal to, or greater than the radius of the cryolesion a completely spherical iceball would theoretically be formed. Pressure on a lesion suspected of malignancy is obviously undesirable because of the possibility of dispersal of tumour cells. However there is advantage in exerting some pressure on a highly vascular benign lesion such as haemangioma in order to reduce blood supply (and heat) brought to the area and thus increase the depth and volume of tissue frozen. A local anaesthetic field block containing vasoconstrictor may also be helpful, as is pressure on the artery supplying the area. The depth of freezing can be reduced by gently lifting the probe once it is frozen to the tissue surface. Changing the angular relationship of the probe to the tissue surface once freezing has commenced is to be
Australian Dental Journal, February, 1976 avoided as the tissue attached to the probe will be snapped off leaving a raw, bleeding surface after thawing. This defeats one of the aims of cryosurgery, namely a bloodless field. Gill, Fraser, Da Costa, and Beazley22 demonstrated that maximum surface contact before lowering the probe temperature produces the greatest radius of freezing. They also showed that with the same probe and freezing temperature, repeated freeze-thaw cycles in the same location produced successively larger iceballs and the rate of freezing was correspondingly increased. This phenomenon seems to be due to an increase in thermal conductivity of the previously frozen tissue. In this way the size of the cryolesion can be increased by repeating the freeze-thaw cycle up to a maximum of five to seven times32. The duration of freezing is obviously significant and Gill and colleagues” found that the volume of tissue frozen bears a logarithmic relation to the duration of freezing. The maximum volume frozen by a given probe and temperature required up to two hours to achieve, but 80-90 per cent of the maximum effect was achieved in the first 15 minutes. Even this period is burdensome under clinical conditions and freezing times of one to four minutes are commonly recommended; the only likely disadvantage being the smaller size of the cryolesion produced. As quoted earlier, Poswill0 31 was of the opinion that tissues subjected to -20°C or below for one minute or more would be destroyed. However, in the same paper he warned against the tendency to over-estimate the amount of destruction produced by the cryoprobe and recommended that “all lesions should be treated by freezing for two minutes and thawing and re-freezing to be certain of achieving a satisfactory tissue ‘kill”’. Thawing is fairly rapid in the mouth, taking no more than a minute or SO under natural conditions. However it can be delayed by compression of the arterial supply and by keeping the lesion exposed to the air. If the iceball is allowed to contact nearby vital teeth intense dental pain can be caused. Cryosurgical equipment with variable temperature would permit prolongation of the thawing process.
Pain Pain is not usually a problem with cryosurgcry and many procedures can be carried out without anaesthesia. However, this is not always predictable and some patients request local anaesthesia after the first freeze-thaw cycle; thawing usually causes more discomfort than freezing and the tongue seems more sensitive than other parts of the mouth. The post-operative period is often
Australian Dental Journal, February, 1976 completely painless but the tongue again can be the principal exception and post-operative analgesics may be needed.
Repeated freeze-thaw cycles Gill, Fraser, and Carter32 made a clear distinction between ,the term “multiple freezing” indicating more than one freeze but at daerent sites, and “repetitive freezing” implying repeated applications of the probe at ,the same site. Similar terminology will be used here. As stated earlier there is the possibility of an escape zone within the boundary of a cryolesion in which cells may survive freezing. It has been suggested that this obstacle might be overcome by employing multipletipped probes that would produce overlapping zones of freezing. Whilst such an instrument may have other advantages, the clinical application of the complex geometry of partially overlapping spheres does not appeal to me and there would still seem to be the possibility of parts of each escape zone not being covered by the lethal zones of adjoining spheres. A more reliable way of dealing with the hypothetical escape zone would be to repeat the freeze-thaw cycle in precisely the same area a number of times. In this way the successive iceballs formed will be concentric and the inner lethal zone of each successive iceball should extend to cover the escape zone of the preceding one. Multiple freeze-thaw cycles Lesions too extensive to be covered by the repetitive freezing technique can be treated by multiple or serial freezing. Thus each part of the lesion will be frozen and thawed two or more times until the whole area has been covered. It is especially desirable to ensure that the entire periphery of the lesion has been adequately treated, particularly if it is thought to be malignant. In the latter case every part of the tumour should be exposed t o at least a triple three minute cryo-cycle30 with adequate time allowed for intermediate thawing. Staging rhe Treatment One of the: advantages of cryosurgery is its flexibility. Large benign lesions may be treated in stages, with areas treated and intervals between treatments scaled to meet the needs of the patient. For example. extensive or multiple haemangiomata or lymphangiomata may be divided into convenient regions so that post-operative swelling and interference with normal function after each treat33
Oill, W., Frsse:, J . , and Carter, D. C.-Repeated freezerthaw cycles in cryosurgery. Nature, 2195152, 410-413 (July) 1968.
41
ment can be confined to one area of the mouth. Staging the treatment of malignant lesions may be contra-indicated because of time lost, unless the lesion is inoperable and cannot be managed by any other means.
used to produce carbon dioxide snow/acetone ‘slush’. Arrow ipdicatu chamois leather
Fig. 3.-Equipment
bu.
Carbon dioxide snow The writer has introduced the use of carbon dioxide snow for the treatment of superficial oral mucosal lesions. It is used either in the solid form as a ‘stick’ that has been compressed in a mould, or with the addition of acetone to form a ‘slush’. Both forms provide a temperature in the vicinity of -80°C; the solid form being slightly colder, but the slush offering greater ease of application. To prepare the slush, carbon dioxide is released from a cylinder (Fig. 3) under pressure into a small chamois leather bag where the expanding gas cools rapidly below its freezing point and solidifies. The resultant ‘snow’ is emptied into a small stainless steel dish and acetone added till the consistency is such that it will adhere to the cotton-tipped end of a swab stick. The adherent mass can be shaped by moulding it against the inside of the bowl to give it a spherical, cylindrical, or angular form or whatever shape is convenient for application to the lesion. Anaesthesia is virtually never required for this form of cryotherapy and no special preparation of the mouth is needed. The refrigerant is touched onto the lesion and each area frozen for 5 to 30 seconds depending on the depth of penetration The freeze-thaw cycle is usually required. repeated at least once. The maximum depth of tissue destruction achieved by this method is of the order of two to three mm. The stick of carbon dioxide snow is generally less convenient to use but has the advantage that
42
it can be applied to the tissue with pressure and thus give slightly greater depth of freezing. The swab-stick technique is particularly useful for treating widespread shallow benign lesions, e.g. extensive leukoplakia that has been demonstrated by biopsy to be benign in nature. Two precautions need to be taken in its use. First, even a well-compacted globule on the swab-stick is still quite friable and should be applied without force, otherwise it may break u p and fall into the mouth. Second, when used toward the back of the mouth, there is considerable 'fogging' of the air in the mouth resulting in loss of visibility. nis can be cleared by the use of an ordinary oral aspirator held near the area under treatment.
Australian Dental Journal, February, 1976 Clinical results are in agreement with Poswil10~~ who observed that less scar tissue was produced than by excision and suture.
Cryorurgery in the mouth Excellent evaluations of the effediveness of cryosurgery in the treatment of oral lesions have been published, Poswillo33, Leopard and Poswill0'4. A wide range of benign lesions lend themselves admirably to treatment. However, special mention should be made of a few that have posed therapeutic problems with conventional techniques, but are amenable to treatment by freezing. The outstanding example of the value of this new technique is in the treatment of angiomatous and other very vascular lesions (Fig. 4). Apart Port-operative course from the troublesome haemorrhage during con'The post-operative period is usually uneven,tful. After shallow freezing patients generally report ventional surgery, the recurrence rate after excicomplete absence of post-operative pain. Deep sion is disturbingly high. Each recurrence requires and extensive freezing (particularly of the tongue) the patient to submit to further surgery and poses can resu1,t in moderate to severe discomfort an ever increasing problem for the surgeon to decide where the boundaries of his next surgical requiring analgesics for a few days. idervention will be. Cryosurgery offers a simple Swelling is usually moderate, begins shortly and effective answer to this problem. Small after thawing, reaches a maximum within 24 lesions usually respond to a double freeze-thaw hours, and requires no special treatment. The cycle and extensive lesions can be treated in exceptions, in my experience, are very vascular appropriate stages (Fig. 5). Recurrences can still lesions and lymphangiomas. These have been occur but pose no problem for re-freezing with observed to swell markedly within minutes of little inconvenience 'to the patient (Fig. 6). Patients treatment (? reactive hyperaemia plus damage to with widespread oral haemorrhagic telangiectasia thin-walled vessels) and to reach impressive pro- who are inconvenienced by repeated bleeding have portions within 24 hours. usually had the troublesome lesions excised or Caution should be observed when freezing areas cauterized and it is alarming to note that some where swelling could interfere with the airway have received repeated radiotherapy for this cone.g. base of tongue, floor of mouth and tonsillar dition. As this is an on-going problem increasing area. In these cases treatment may be staged or with age, the ease and convenience of treatment if this is contra-indicated the patient should be with cryosurgery is a boon to them (Fig. 7). admitted to hospital for treatment and post- Multiple pregnancy tumours offer a further operative observation. example of vascular lesions with a high recurrence With ordinary post-operative care, infection of ra,te that lend themselves to cryotherapy. the cryolesion is rare and is seen less frequen,tly Papillomatosis of the palate is a lesion that has than after conventional surgery. Post-operative provided therapeutic problems for both patient haemorrhage is exceedingly rare; however it must and surgeon. Conventional surgical excision is be recognised as a possible sequel to infection. technically difficult, dermabrasion is bloody and When examined two to three days after surgery lacking in finesse, and electrocautery is malodourthe cryolesion is usually covered by a yellow-grey ous and disturbing for the patient. All these slough and its margins are demarcated from the procedures also result in considerable postsurrounding tissue. There is surprisingly little operative pain. Cryosurgery offers a simple techinflammatory reaction to be seen in the adjacent nique, a bloodless field and little post-operative tissue. Irrigations with dilute hydrogen peroxide discomfort. and other antiseptic mouthwashes help to remove The third type of lesion that merits special sloughing tissue and keep ,the mouth in a pleasant mention is widespread leukoplakia of ,the oral state. Epithelialisation of soft tissue wounds takes from as little as 10 days up to seven weeks, depending on the size of the area treated. In 33 Poswillo, D. E.-Cryosurgery in and around the oral cavity. I n , Recent advances in surgery. Edit. Taylor S. general, scarring is minimal following cryosurgery. London, Churchill-Livingstone, 1973 (pp. 69-101).
Australian Dental Journal, February, 1976 cavity that is too extensive for removal by conventional surgery or in areas that do not lend themselves to excision (Fig. 8). Electro-surgery is to be avoided because of the subsequent warring and the high incidence of recurrence of the
43
spread shallow lesions. The use of carbon dioxide/ acetone slush has proved simple and effective for the removal of superficial leukoplakia. Recurrence is rare (except when the aetiological factor e.g. smoking, has not been eliminated) and there
Fig. 4 . 4 4 Two haemangiomas right ride of tongue partly thawed after freaing. (b) Sama area four weeks after cryosurgery.
Fig. 5 . 4 . ) One area in the mouth of a young patient with lymphanpiomas in several locations. (b) Same region showing well demarcated sloughing area. (c) Same region almost healed. four weeks after cryosurgery.
original lesion. All leukoplakia of the mouth must first be carefully evaluated and its true nature determined (usually by biopsy). If the lesion does not then respond to conservative treatment the least that should be done is to keep the lesion(.$ under long-term surveillance. However cryosurgery now permits the removal of such wide-
is no discernible scarring. Biopsy can be carried out at any time and can be done whilst the tissues are partially frozen. Apart from the treatment of proliferative lesions, cryosurgery has some place in the trea,tment of ulcerative and erosive lesions. Erosive lichen planus is not characterised by pain except
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Australian Dental Journal, February, 1976
Fig. 6 . 4 a ) Haemangioma, tip of tongue. (b) Same area with partial recurrence right side four weeks after cryosurgery. (c) Same area, healed and free of haemangioma, three weeks later.
Fig. 7 . 4 6 Patient with. haemorrhagic telangiectasia. The lesion in the centre of the tongue bothered the patient because of spontaneous bleeding. (b) The lesion during thawing. (c) Same area three weeks after cryosurgery.
Australian Dental Journal, February, 1976 when secondarily infected, usually by candida albicans. Nevertheless the lesions cause discomfort and should not be permitted to continue indefinitely because of possible malignant transformation. Personal experience has shown cryo-
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usefulness in certain circumstances. In 1%5 Gage, Koepf, Wehrle, and Emmingsz reported the successful treatment of malignancy in the mouths of four specially selected patients who had lesions resistant to radiotherapy, lesions in areas not
Fig. 8 . 4 8 ) One of many patch- of leukoplakia in unusual locations in the one mouth and not particularly amenable to surgical excision. (b) Same area free of leukoplakia three wceks after treatment with COnIacetone.
surgical treatment of these erosions to be reasonably successful. Many heal with new healthy epithelium advancing across the lesions some two to three weeks after treatment. On the other hand, it has been disappointing to see recurrence of erosions in some of the areas treated. The anatomical locations of some lesions present problems for conventional surgery and electrosurgery but are amenable to a cryosurgical approach. Lesions involving the free marginal gingivae, or vermilion border of the lip can USUally be eliminated without loss of contour and natural colour. Conventional excision of lesions in the buccal or lingual sulci often results in loss of valuable depth. On the other hand, cryodestruction usually causes little or no loss of sulcus depth. Premalignant lesions that have progressed to the stage of epithelial dysplasia and that are too extensive for conventional surgical excision can be adequately treated with cryosurgery. The use of carbon dioxide snow may not give sufficient depth of freezing and use of a cryosurgical probe is indicated. All parts of the lesion should be subjeuted to two or three freezes of two minutes each with adequate intervals for thawing. Poswill# reported the recurrence of dyskeratotic lesions following electrosurgery and favours the use of cryosurgery.
Mnllsp.nt oral lesions writer has not used CryOsUrgery for the treatment of malignant lesions but recognises its
amenable to excision without disabling surgery, or severe cardiac disease. Gage and KoepP4 later reported on a much larger group of patients and concluded that the results were comparable with whet might have been expected of excision. The main advantages were that the technique was especially suitable for poor risk patients and mutilating operations were avoided. Cherry% obtained excellent short-term results with cryotherapy for four patients with oral carcinoma in whom the prognosis was extremely poor, yet he gave only guarded commendation of the technique. Poswillo33 found cryosurgery of considerable value in the palliative treatment of recurrent oral cancer, in the treatment of metastatic nodes adherent to major vessels and nerves and in attempts to treat large inoperable lesions. He was particularly impressed by its effectiveness in controlling intractable pain. Poswillo also appears to give some credence to the theory that immune response is invoked or at least enhanced by cryodestruction of tumour tissue and quoted Neel, Ketcham and Hammond36 whose work on transplanted tumours in animals demonstrated that in
34Gw, A. A.. and Koepf, S. W.-Cryotherapy as primary treatment for oral cancer. J. Cryosurg., 1: 177-183, 1966. 35 Cherry, J.-Cryosurgery of oral cancer. Arch. Otolaryng., 91:6, 548-551 (June) 1970.
€B.. I. Ketcham, A. s., and Harnrnond. W. 0.Requisites for SuCCeSSful cry0 nic surgery of cancer. Arch. Sbrg., 102:1, 4548 (Jan.$1971.
36N-1,
46 situ tumour destruction by freezing provides greater immunity to subsequent tumour challenge than does tumour removal by excision”. In summary then, it seems that whilst cryosurgery does not replace conventional methods of treatment for oral malignancy, the technique has proven value and possibly unassessed potential. At least it offers hope for poor risk patients and those with lesions beyond the range of surgery or radiotherapy. When dealing with excisable or radiosensitive lesions the disadvantages of cryosurgery must be considered. These include the difficulty of accurately assessing the margins of cryodestruction in three dimensions and the lack of a complete surgical specimen for histological examination.
Discussion Cryosurgery is a form of treatment that enables local destruction of tissue by simple means. There can be n o question of its superiority over conventional methods of surgery for the treatment of certain benign and premalignant oral lesions. The prime examples are angiomatous lesions, palatal papillary hyperplasia and widespread leukoplakia (with or without epithelial dysplasia). In the field of oral malignancy, cryosurgery has largely been used after other forms of treatment have failed or where the patient or the tumour have not been considered suitable for conventional therapy. Numerous successes have been reported and at least it offers palliation and relief of pain. Apart from the ischaemic infarction produced by freezing tissues, the methods by which cells are destroyed by intense cold are complex and as yet poorly understood. There is agreement that many potentially destructive processes contribute to cell death but as yet the relative contribution of each process has not been evaluated. The most disturbing aspect of our current lack of knowledge is that it has not been possible to establish firm criteria that will ensure the certain destruction of all cells in a given zone. On the one hand several eminent authorities have suggested that under cryosurgical conditions (rapid freeze-slow thaw) all cells cooled to the vicinity of -20°C will die; on the other, it is disconcerting t o find good experimental evidence36 that under similar conditions, effective tumour control required repetitive freezing of tissues to temperatures below -60°C. When it is also borne in mind that the temperature gradient in tissue adjacent to the probe tip is extremely steep21 (e.g. -190°C at probe tip and only -56°C 2 mm away) it becomes obvious that
Australian Dental Journal, February, 1976 improved equipment, and extremely low temperatures will be needed before cryosurgery can be confidently used for the primary treatment of oral cancer. Another disadvantage of cryosurgery in the treatment of malignant lesions is the lack of a postsurgical specimen for histological examination. It is true that in conventional cold knife excision the surgeon still has to estimate the boundaries of the lesion, but the entire specimen is available post-operatively when these boundaries can be examined histologically. It has also been claimed by numerous authors that the extent of the cryolesion is predictable and reproducible, but in my estimation nothing could be further from the truth. It may well be that under experimental conditions, predictable and reproducible cryolesions can be produced in one animal after another. However, a great deal more clinical experience is required in the treatment of oral lesions, ideally with probe-thermocouple monitoring of tissue temperatures at known distances below and lateral to the probe tip. A vast amount of such data will be necessary for the various parts of the mouth and taking into account all other variables, before accurately predictable cryolesions can be anticipated. The advantages of cryosurgery are many. Preparation of the patient and the mouth are minimal and equipment and techniques are simple. It has minimal phychological effect upon the patient and does not raise the fears associated with other forms of surgery. Operating times are short and can be scaled to the needs of the patient. Because it produces so little mental and physical stress, it is well suited to the poor risk patient. It offers tissue destruction without haemorrhage and with little operative or post-operative discomfort. Postoperative infection and other complications are rare and scar tissue formation is minimal and usually soft in nature. When the vermilion border of the lip is involved in the cryolesion there is usually restoration of form and normal colour after healing. The possibility that freezing of tumour tissue may change it in such a way (physically or chemically) that it will act as an auto-antigen and provide or intensify an antibody reaction is exceedingly attractive. Whilst there is very limited evidence to support this concept at present, it must command the attenion of all who work in the field of immunology. There is already acceptance of the concept that if ways can be found to induce the body to recognise tumour tissue as ‘non-self‘ and produce antibodies to its own tumour tissue, this would provide the ultimate in cancer therapy.
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Australian Dental Journal, February, 1976 1.t may well be that some means will be found to intensify the antigenic stimulus of freezing. One of the advantages ascribed to cryodestruction of a lesion is that it ‘fixes’ cells within the iceball thus preventing dissemination of tumour cells during surgery. This is almost certainly a valid attribute of the technique, but it is possible that the immediate post-thawing hyperaemia2c could be intense enough to disseminate tumour cells, particularly in lesions large enough to require repetitive freezing. If this were so, preoperative field block of the area with anaesthetic containing adrenaline may minimise the reactive hyperaemia. Carbon dioxide snow has been used with obvious success for many years in the field of dermatology for the treatment of superficial lesions, notably solar keratoses. The writer has used similar techniques for the treatment of widespread shallow oral lesions. The prime example is widespread leukoplakia that has been investigated by biopsy and found to be innocent in nature. Anaesthesia has not been necessary, postoperative discomfort is virtually nil and results have been gratifying. Its virtues are simplicity
and ease of application and the short clinical time involved in its application. There is no discernible scarring following its use and the usual result is restoration of normal, healthyappearing mucosa.
Condualon Cryosurgery adds a comparatively new therapeutic technique to the repertoire of the dental and oral surgeon. It does not replace conventional methods of treatment except for a small number of special lesions. However it has an unquestionable contribution to make in the treatment of a wide range of benign and premalignant lesions and in the management of malignant lesions in highly selected patients, 1.t should be used with discretion however and where the nature of the lesion is in doubt it should be left in the hands of the appropriate specialist. Department of Oral Medicine and Oral Surgery, University of Sydney, 2 Chalmers Street, Surry Hills, N.S.W.2010
Malnutrition National mortality statistics rarely mention undernutrition as a cause of death. The Inter-American Investigation of Mortality in Childhood, conducted in 18 widely dif€ering areas of the Americas and sponsored by the Pan American Health Organization, indicated that malnutrition was the underlying cause of death in children under 5 years in 7% of cases and an associated cause in 46.2% of cases.-W.H.O. Geneva, VoZ. 29, October, 1975.
