0360-3016/90 $3.00 + .Xl Copyright Q 1990 Pergamon Press plc
Inl. I Radiation Oncdogy Bid Phys., Vol. IS, pp. 1535-1536 Printed in the U.S.A. All rights reserved.
??Correspondence
REPLY
TO DR. WANG’S
part of the normal supraglottic larynx. I surmise that what is primarily meant is unnecessary irradiation of the glottic larynx. I agree that for radiation therapy for carcinomas of the nasopharynx and oral cavity for instance, the glottic and subglottic larynx should not be included within the high dose irradiated volume through large lateral portals as the lymph node disease in the mid and lower neck can be easily handled by separate anterior portal with midline tracheal and spinal cord block. Contrary to the practice of Mendenhall et al., I have used I .5 cm instead of 0.5 cm wide block for many years and found it to be perfectly satisfactory without a single case of midline recurrence. On the other hand, for the comprehensive irradiation of the base of the tongue and faucial tonsil, the supraglottic structures must be included within the target volume but sparing the glottis and arytenoids. One of the useful landmarks for head and neck irradiation is the thyroid notch. If the inferior border of the lateral portals is placed above the thyroid notch level, one can be reasonably certain that the glottis and the arytenoids are out of the irradiated field and yet the subdigastric nodes are adequately included. The normal larynx can tolerate a dose of 45 to 50 Gy by conventional fractionation without lasting consequences. With further increase of dose up to 68-75 Gy to the entire larynx, arytenoidal edema of varying extent may occur. In severe cases it may become symptomatic and lasting, that is, laryngeal irritation, hoarseness, dysphagia, among others. Therefore, care must be taken to spare the normal arytenoids from high dose effects through the shrinking field technique. Mendenhall et al. present a worst case scenario of inhomogeneity in irradiating the larynx in Figure 1D. This could be prevented by using compensated, or contour wedges and careful treatment planning. With understanding of radiation tolerance of normal organs, the serious radiation complications as indicated in the editorial, such as radiation myelitis and necrosis of the larynx, rarely occur after modem radiation therapy but they should be avoided at all costs.
EDITORIAL
To the Editor: I agree with Dr. Wang that intraoral cone radiotherapy is a viable and often times preferable alternative to interstitial therapy as a boost technique. There may be favorable subsets of lesions that are treatable with intraoral cone irradiation such as less infiltrative or smaller cancers. However, in lesions that are suitable for intraoral irradiation Dr. Wang has obtained excellent control rates equivalent to those obtained with radiotherapy techniques where the majority of therapy is delivered with interstitial therapy (75-92% for Stage TzNo oral tongue cancers) (1, 2, 4) with very low complication rates (3). For patients referred to our department for definitive therapy our current policy is to deliver boost therapy with intraoral cone irradiation when technically feasible. Various characteristics of interstitial therapy have been postulated as the reason interstitial therapy is more efficient than external beam therapy. These include continuous low dose rate, the shorter time necessary to deliver the total dose, and “hot spots” near sources in the treatment volume. The effectiveness of intraoral cone therapy seems to indicate that shortened treatment time may be the most important factor. CHARLES D. WENDT, M.D.
The University of Texas M. D. Anderson Cancer Center Houston. TX 77030 Mazeron, C. E.; Martin, M.; Maylin, C.; Le Beourgeuis, J. P.; Lobo, P.; Baillet, F.; Pierquin, B. Analysis of local failures after treatment with curie therapy for squamous cell carcinomas of the oral tongue. J. Eur. Radiother. 3:131-138; 1982. Mendenhall, W. M.; Parsons, J. T.; Stringer, S. P.; Cassisi, N. J.; Million, R. R. Tz oral tongue carcinoma treated with radiotherapy: analysis of local control and complications. Radiother. Oncol. 16: 275-281; 1989. Wang, C. C. Radiotherapeutic management and results of T,No TzNo carcinoma of the oral tongue: Evaluation of boost techniques. Int. J. Radiat. Oncol. Biol. Phys. 17:287-291; 1989. Wendt, C. D.; Peters, L. J.; Delclos, L.; Ang, K. K.; Morrison, W. H.; Maor, M. H.; Byers, R. M.; Carbon, L. S.; Oswald, M. J. Primary radiotherapy in the treatment of Stage I and II oral tongue cancers: importance of the proportion of therapy delivered with interstitial therapy. Int. J. Radiat. Oncol. Biol. Phys. 18:1287-1292; 1990.
KEEPING
THE ARYTENOID
C. C. WANG, M.D. Department of Radiation Medicine Massachusetts General Hospital Boston, MA 02 114
CRITIQUE OF “STEREOTACI’IC RADIOSURGERY FOR INTRACRANIAL ARTERIOVENOUS MALFORMATIONS USING A STANDARD LINEAR ACCELERATOR”
To the Editor: In a recent article by Loeffler et al. (3) a dose response relationship is displayed in Figure 1. These data were used as a basis for choosing the dose to treat arteriovenous malformations. The figure was difficult to understand because there was no legend to explain what the symbols represented. It was not until one looked at the article by Kjehberg ef al. (2), where the data were originally published, that you realized what the symbols represented. Since radiosurgery is a relatively new, untried technique the use of any dose response relationship should be looked at critically. The data of Kjellberg et al. referred to their experience with the proton beam. It can be presumed that their patients were treated to a uniform dose of 100% throughout the target volume. It appears that Loeffler et al. prescribes their dose to the 80% isodose. It is hard to evaluate what effect the 20% increase in dose at the maximum makes. When the data in Figure I are analyzed using the point-biserial correlation (RPB) analysis (1) there seems to be little correlation between dose and complications. Table 1 summarizes the results. If all complications are analyzed then a positive correlation of 0.4% is found. Thus, 99.6% of the change in complications is not explained by a change in
DOSE LOW
To the Editor: The obvious goal of radiation therapy for head and neck carcinomas is to maximize locoregional control and to minimize late radiation complications. Any large portal irradiation which unnecessarily includes the neighboring non-target normal organs or tissues should be discouraged. However, since most squamous cell carcinomas tend to infiltrate the surrounding tissues, unusually small field radiation techniques may result in geographic misses followed by local failure. Therefore, the selection of appropriate portal size and shape for radiotherapy of any particular lesion is, at times, extremely difficult and ir often a personal preference derived from experience. As in all medicine, frequently the parochial “standard” treatment in one’s practice may not be considered standard by some and, at times, is unacceptable to others. In this issue of the journal, the editorial comments by Mendenhall et al. remind us of avoiding unnecessary irradiation of normal tissues and larynx (shown in Fig. I A). Unfortunately, Figure I B does not coincide well with the title of the editorial as the portal shown includes a large 1535
1536
I. J. Radiation Oncology 0 Biology 0 Physics
dose. A slightly higher correlation is found when only the serious complications are analyzed (0.7%). When the beam diameter is correlated with complications the negative sign means the smaller beam diameter correlated with more complications but to a very small extent (0.2%).
Table 1. Treatment complications
of arteriovenous malformation vs dose or beam diameter
3. Loeffler, J. S.; Alexander III, E.; Siddon, R. L.; Saunders W. M.; Coleman, C. N.; Winston, K. R. Stereotactic radiosurgery for intracranial arteriovenous malformations using a standard linear accelerator. Int. J. Radiat. Oncol. Biol. Phys. 17:673-677; 1989.
RESPONSE
Condition
Sign of RPB
RPB2 90
All complications Serious complications Beam diameter
+ + _
0.4 0.7 0.2
Thus, the data show a very weak correlation with dose or beam diameter and complications. The lines drawn through the data at 99% and 1% for isoeffect doses should be treated very cautiously. We should not get overconfident just because statisticians can draw lines through data that represent isoeffective doses. With more data perhaps very different results would occur. Our comments should not detract from the importance of this article. Radiosurgery is a new technique. This paper is unique in the number of patients treated and the excellence of the follow-up. We are indebted to this study because we and others do not have to start at the beginning but can use this pioneering study as a landmark. MYRON WOLLIN, M.S.
Radiation Physicist ANAND KURUVILLA,
June 1990, Volume 18, Number 6
M.D.
Radiation Oncologist A. R. KAGAN, M.D. Chief, Radiation Oncology Department ARTHUR OLCH,
PH.D. Radiation Physicist Southern California Permanente Medical Group Los Angeles, CA 90027 I. Bruning, J. L.; Kintz, B. L. Computational handbook of statistics. Glenview, IL: Scott, Foresman; 1968. 2. Kjellberg, R. K.; Hanamura, T.; Davis, K. R.; Lyons S. L.; Adams, R. L. Bragg-peak proton-beam therapy for arteriovenous malformations of the brain. N. Engl. J. Med. 309:269-274; 1983.
TO WOLLIN et al.
To the Editor: On behalf of all the authors, we would like to thank Wollin et al. for their interest and thoughtful comments about our recent paper. We would like to take this opportunity to respond to several important points raised in their letter: I. In our experience treating small arteriovenous malformations (
Inl. I Radiation Oncdogy Bid Phys., Vol. IS, pp. 1535-1536 Printed in the U.S.A. All rights reserved.
??Correspondence
REPLY
TO DR. WANG’S
part of the normal supraglottic larynx. I surmise that what is primarily meant is unnecessary irradiation of the glottic larynx. I agree that for radiation therapy for carcinomas of the nasopharynx and oral cavity for instance, the glottic and subglottic larynx should not be included within the high dose irradiated volume through large lateral portals as the lymph node disease in the mid and lower neck can be easily handled by separate anterior portal with midline tracheal and spinal cord block. Contrary to the practice of Mendenhall et al., I have used I .5 cm instead of 0.5 cm wide block for many years and found it to be perfectly satisfactory without a single case of midline recurrence. On the other hand, for the comprehensive irradiation of the base of the tongue and faucial tonsil, the supraglottic structures must be included within the target volume but sparing the glottis and arytenoids. One of the useful landmarks for head and neck irradiation is the thyroid notch. If the inferior border of the lateral portals is placed above the thyroid notch level, one can be reasonably certain that the glottis and the arytenoids are out of the irradiated field and yet the subdigastric nodes are adequately included. The normal larynx can tolerate a dose of 45 to 50 Gy by conventional fractionation without lasting consequences. With further increase of dose up to 68-75 Gy to the entire larynx, arytenoidal edema of varying extent may occur. In severe cases it may become symptomatic and lasting, that is, laryngeal irritation, hoarseness, dysphagia, among others. Therefore, care must be taken to spare the normal arytenoids from high dose effects through the shrinking field technique. Mendenhall et al. present a worst case scenario of inhomogeneity in irradiating the larynx in Figure 1D. This could be prevented by using compensated, or contour wedges and careful treatment planning. With understanding of radiation tolerance of normal organs, the serious radiation complications as indicated in the editorial, such as radiation myelitis and necrosis of the larynx, rarely occur after modem radiation therapy but they should be avoided at all costs.
EDITORIAL
To the Editor: I agree with Dr. Wang that intraoral cone radiotherapy is a viable and often times preferable alternative to interstitial therapy as a boost technique. There may be favorable subsets of lesions that are treatable with intraoral cone irradiation such as less infiltrative or smaller cancers. However, in lesions that are suitable for intraoral irradiation Dr. Wang has obtained excellent control rates equivalent to those obtained with radiotherapy techniques where the majority of therapy is delivered with interstitial therapy (75-92% for Stage TzNo oral tongue cancers) (1, 2, 4) with very low complication rates (3). For patients referred to our department for definitive therapy our current policy is to deliver boost therapy with intraoral cone irradiation when technically feasible. Various characteristics of interstitial therapy have been postulated as the reason interstitial therapy is more efficient than external beam therapy. These include continuous low dose rate, the shorter time necessary to deliver the total dose, and “hot spots” near sources in the treatment volume. The effectiveness of intraoral cone therapy seems to indicate that shortened treatment time may be the most important factor. CHARLES D. WENDT, M.D.
The University of Texas M. D. Anderson Cancer Center Houston. TX 77030 Mazeron, C. E.; Martin, M.; Maylin, C.; Le Beourgeuis, J. P.; Lobo, P.; Baillet, F.; Pierquin, B. Analysis of local failures after treatment with curie therapy for squamous cell carcinomas of the oral tongue. J. Eur. Radiother. 3:131-138; 1982. Mendenhall, W. M.; Parsons, J. T.; Stringer, S. P.; Cassisi, N. J.; Million, R. R. Tz oral tongue carcinoma treated with radiotherapy: analysis of local control and complications. Radiother. Oncol. 16: 275-281; 1989. Wang, C. C. Radiotherapeutic management and results of T,No TzNo carcinoma of the oral tongue: Evaluation of boost techniques. Int. J. Radiat. Oncol. Biol. Phys. 17:287-291; 1989. Wendt, C. D.; Peters, L. J.; Delclos, L.; Ang, K. K.; Morrison, W. H.; Maor, M. H.; Byers, R. M.; Carbon, L. S.; Oswald, M. J. Primary radiotherapy in the treatment of Stage I and II oral tongue cancers: importance of the proportion of therapy delivered with interstitial therapy. Int. J. Radiat. Oncol. Biol. Phys. 18:1287-1292; 1990.
KEEPING
THE ARYTENOID
C. C. WANG, M.D. Department of Radiation Medicine Massachusetts General Hospital Boston, MA 02 114
CRITIQUE OF “STEREOTACI’IC RADIOSURGERY FOR INTRACRANIAL ARTERIOVENOUS MALFORMATIONS USING A STANDARD LINEAR ACCELERATOR”
To the Editor: In a recent article by Loeffler et al. (3) a dose response relationship is displayed in Figure 1. These data were used as a basis for choosing the dose to treat arteriovenous malformations. The figure was difficult to understand because there was no legend to explain what the symbols represented. It was not until one looked at the article by Kjehberg ef al. (2), where the data were originally published, that you realized what the symbols represented. Since radiosurgery is a relatively new, untried technique the use of any dose response relationship should be looked at critically. The data of Kjellberg et al. referred to their experience with the proton beam. It can be presumed that their patients were treated to a uniform dose of 100% throughout the target volume. It appears that Loeffler et al. prescribes their dose to the 80% isodose. It is hard to evaluate what effect the 20% increase in dose at the maximum makes. When the data in Figure I are analyzed using the point-biserial correlation (RPB) analysis (1) there seems to be little correlation between dose and complications. Table 1 summarizes the results. If all complications are analyzed then a positive correlation of 0.4% is found. Thus, 99.6% of the change in complications is not explained by a change in
DOSE LOW
To the Editor: The obvious goal of radiation therapy for head and neck carcinomas is to maximize locoregional control and to minimize late radiation complications. Any large portal irradiation which unnecessarily includes the neighboring non-target normal organs or tissues should be discouraged. However, since most squamous cell carcinomas tend to infiltrate the surrounding tissues, unusually small field radiation techniques may result in geographic misses followed by local failure. Therefore, the selection of appropriate portal size and shape for radiotherapy of any particular lesion is, at times, extremely difficult and ir often a personal preference derived from experience. As in all medicine, frequently the parochial “standard” treatment in one’s practice may not be considered standard by some and, at times, is unacceptable to others. In this issue of the journal, the editorial comments by Mendenhall et al. remind us of avoiding unnecessary irradiation of normal tissues and larynx (shown in Fig. I A). Unfortunately, Figure I B does not coincide well with the title of the editorial as the portal shown includes a large 1535
1536
I. J. Radiation Oncology 0 Biology 0 Physics
dose. A slightly higher correlation is found when only the serious complications are analyzed (0.7%). When the beam diameter is correlated with complications the negative sign means the smaller beam diameter correlated with more complications but to a very small extent (0.2%).
Table 1. Treatment complications
of arteriovenous malformation vs dose or beam diameter
3. Loeffler, J. S.; Alexander III, E.; Siddon, R. L.; Saunders W. M.; Coleman, C. N.; Winston, K. R. Stereotactic radiosurgery for intracranial arteriovenous malformations using a standard linear accelerator. Int. J. Radiat. Oncol. Biol. Phys. 17:673-677; 1989.
RESPONSE
Condition
Sign of RPB
RPB2 90
All complications Serious complications Beam diameter
+ + _
0.4 0.7 0.2
Thus, the data show a very weak correlation with dose or beam diameter and complications. The lines drawn through the data at 99% and 1% for isoeffect doses should be treated very cautiously. We should not get overconfident just because statisticians can draw lines through data that represent isoeffective doses. With more data perhaps very different results would occur. Our comments should not detract from the importance of this article. Radiosurgery is a new technique. This paper is unique in the number of patients treated and the excellence of the follow-up. We are indebted to this study because we and others do not have to start at the beginning but can use this pioneering study as a landmark. MYRON WOLLIN, M.S.
Radiation Physicist ANAND KURUVILLA,
June 1990, Volume 18, Number 6
M.D.
Radiation Oncologist A. R. KAGAN, M.D. Chief, Radiation Oncology Department ARTHUR OLCH,
PH.D. Radiation Physicist Southern California Permanente Medical Group Los Angeles, CA 90027 I. Bruning, J. L.; Kintz, B. L. Computational handbook of statistics. Glenview, IL: Scott, Foresman; 1968. 2. Kjellberg, R. K.; Hanamura, T.; Davis, K. R.; Lyons S. L.; Adams, R. L. Bragg-peak proton-beam therapy for arteriovenous malformations of the brain. N. Engl. J. Med. 309:269-274; 1983.
TO WOLLIN et al.
To the Editor: On behalf of all the authors, we would like to thank Wollin et al. for their interest and thoughtful comments about our recent paper. We would like to take this opportunity to respond to several important points raised in their letter: I. In our experience treating small arteriovenous malformations (
