CORRESPONDENCE
Ann Thorac Surg
687
1990;50684-8
On the other hand, and most importantly, Dr Mulder and I are in complete agreement that whatever surgical technique is employed, extreme care must be taken to avoid injury (direct trauma or cautery) to both phrenic nerves, the left vagus nerve in the chest, and both recurrent laryngeal nerves in the neck even if in protecting these nerves some microscopic thymus is left behind.
Alfred Iaretzki I l l , M D Thoracic Surgical Section Columbia-Presbyterian Medical Center 161 Fort Washington Ave New York, N Y 10032
References 1. Mulder DG, Graves M, Herrmann C. Thymectomy for myasthenia gravis: recent observations and comparison with past experience. Ann Thorac Surg 1989;48:551-5. 2. Jaretzki A 111. Thymectomy for myasthenia gravis [Letter]. Ann Thorac Surg 1990;49:688. 3. Mulder DG. Thymectomy for myasthenia gravis. Reply [Letter]. Ann Thorac Surg 1990;49:688. 4. Jaretzki A 111, Wolff M. "Maximal" thymectomy for myasthenia gravis: surgical anatomy and operative technique. J Thorac Cardiovasc Surg 1988;96:711-6. 5. Jaretzki A 111, Penn AS, Younger DS, et al. "Maximal" thymectomy for myasthenia gravis: results. J Thorac Cardiovasc Surg 1988;95:747-57.
Reply
To the Editor:
Doctor Jaretzki and associates have offered their reasoning for excluding three groups of patients with myasthenia gravis rather than reporting their entire experience with "maximal" thymectomy. Our report contained all patients including those with thymomas, and some reoperations on patients who had no improvement after a cervical or possibly incomplete transsternal thymectomy, and even those operated on relatively recently who might be expected to improve with time-this latter group comprising almost one fourth of Jaretzki's entire series (29/124) being "not available for analysis" 2 to 3 years after operation. In addition it would have seemed to us that a strong case could be made for "maximal" thymectomy if in the 8 patients undergoing reoperation for failed (incomplete?) thymectomy, residual thymic tissue had been found in aberrant locations (neck, aorticopulmonary window, etc) and these patients had shown improvement. To exclude them as a "select group of patients . . . [that] represent an entirely different patient mix" would seem inconsistent with his subsequent sentence stating that "some investigators believe they will not be helped by reoperation, although in our experience they are." Doctor Jaretzki quite correctly reminds us that great care must be taken to not injure the phrenic, vagus, and recurrent laryngeal nerves as these injuries are especially devastating in the patient with myasthenia gravis. Such injuries are most likely to occur while dissecting in the neck. As mentioned in our previous response, Dr Jaretzki and associates have made a substantial contribution with their cadaver studies showing the aberrant locations in which thymic tissue has been found. It may be that for those occasional patients with severe residual or recurrent myasthenia in whom one has done the transsternal, "complete" thymectomy that we have described, a transsternal reexploration with a concomitant cervical incision and exploration could be considered while recognizing the increased morbidity associated with this. We remain
unconvinced that such a "maximal" thymectomy should be considered the procedure of choice for all patients with myasthenia gravis.
Donald G. Mulder, M D Division of Cardiothoracic Surgery UCLA School of Medicine Center for the Health Sciences 10833 Le Conte Ave Los Angeles, C A 90024-1741
Intraoperative Photodynamic Therapy for Malignant Mesothelioma To the Editor: We read with interest the article by Watts and colleagues entitled "Giant benign mesothelioma" [l], and we would like to bring to your attention a new approach that is being investigated at our institution for the possible management of diffuse pleural malignant mesothelioma. This approach involves the preoperative delivery of a photosensitizer (dihematoporphyrin ether) and debulking of disease to 5 mm thickness, either by pleurectomy or extrapleural pneumonectomy, followed by intraoperative delivery of 630-nm light using an argon pump-dye laser. This therapy, known as photodynamic therapy, is based on the in vivo selective retention of sensitizer by malignant tissue and relatively superficial depth penetration of light wavelengths (5 to 7 mm), which may be useful in the treatment of surface malignancies (neoplasms of skin, bladder, bronchus, and esophagus) [2]. We recently treated a 58-year-old man with right-sided diffuse pleural mesothelioma by performing an extrapleural pneumonectomy 2 days after he received 2.0 mg/kg of dihematoporphyrin ether. After the diaphragm was replaced with dura mater, the only areas of gross residual disease included the lateral chest wall at the diaphragmatic sulcus, and these areas were debulked to 5 mm thickness or less. After hemostasis was obtained, seven sterile photodiodes were sewn to the chest cavity superiorly (I), inferiorly (2), medial, lateral, and posteriorly (1 each), and one photodiode was secured to the right ventricular epicardium. These photodiodes were then attached to a continuously integrating computerized photometer for instantaneous and cumulative recording of light power density and integrated energy density from the areas monitored by the photodiodes. The chest cavity was then filled with 0.02% intralipid for light scattering, and pleural illumination was accomplished with two specially instrumented laser fibers, one each from two lasers. Seven watts of continuous 630-nM light was used to deliver a total dose of 15 J/cm2to the chest cavity. The heart was treated to a total dose of 11J/cm2.After light delivery the photodiodes were removed, and the chest was closed without drainage. Total operative time was 8 hours, with 37 minutes of laser time. The patient was extubated the following morning. The only evidence of substantial chemical abnormality included a rise in the serum creatinine level from 90 to 140 Fmol/L (1.0 to 1.6 mg/dL) on the night of operation, which normalized with hydration over the next 48 hours, and a rise in the creatine kinase level from a baseline of 44 to 11,030 U/L 72 hours after photodynamic therapy. Myoglobin was absent from the urine (
Ann Thorac Surg
687
1990;50684-8
On the other hand, and most importantly, Dr Mulder and I are in complete agreement that whatever surgical technique is employed, extreme care must be taken to avoid injury (direct trauma or cautery) to both phrenic nerves, the left vagus nerve in the chest, and both recurrent laryngeal nerves in the neck even if in protecting these nerves some microscopic thymus is left behind.
Alfred Iaretzki I l l , M D Thoracic Surgical Section Columbia-Presbyterian Medical Center 161 Fort Washington Ave New York, N Y 10032
References 1. Mulder DG, Graves M, Herrmann C. Thymectomy for myasthenia gravis: recent observations and comparison with past experience. Ann Thorac Surg 1989;48:551-5. 2. Jaretzki A 111. Thymectomy for myasthenia gravis [Letter]. Ann Thorac Surg 1990;49:688. 3. Mulder DG. Thymectomy for myasthenia gravis. Reply [Letter]. Ann Thorac Surg 1990;49:688. 4. Jaretzki A 111, Wolff M. "Maximal" thymectomy for myasthenia gravis: surgical anatomy and operative technique. J Thorac Cardiovasc Surg 1988;96:711-6. 5. Jaretzki A 111, Penn AS, Younger DS, et al. "Maximal" thymectomy for myasthenia gravis: results. J Thorac Cardiovasc Surg 1988;95:747-57.
Reply
To the Editor:
Doctor Jaretzki and associates have offered their reasoning for excluding three groups of patients with myasthenia gravis rather than reporting their entire experience with "maximal" thymectomy. Our report contained all patients including those with thymomas, and some reoperations on patients who had no improvement after a cervical or possibly incomplete transsternal thymectomy, and even those operated on relatively recently who might be expected to improve with time-this latter group comprising almost one fourth of Jaretzki's entire series (29/124) being "not available for analysis" 2 to 3 years after operation. In addition it would have seemed to us that a strong case could be made for "maximal" thymectomy if in the 8 patients undergoing reoperation for failed (incomplete?) thymectomy, residual thymic tissue had been found in aberrant locations (neck, aorticopulmonary window, etc) and these patients had shown improvement. To exclude them as a "select group of patients . . . [that] represent an entirely different patient mix" would seem inconsistent with his subsequent sentence stating that "some investigators believe they will not be helped by reoperation, although in our experience they are." Doctor Jaretzki quite correctly reminds us that great care must be taken to not injure the phrenic, vagus, and recurrent laryngeal nerves as these injuries are especially devastating in the patient with myasthenia gravis. Such injuries are most likely to occur while dissecting in the neck. As mentioned in our previous response, Dr Jaretzki and associates have made a substantial contribution with their cadaver studies showing the aberrant locations in which thymic tissue has been found. It may be that for those occasional patients with severe residual or recurrent myasthenia in whom one has done the transsternal, "complete" thymectomy that we have described, a transsternal reexploration with a concomitant cervical incision and exploration could be considered while recognizing the increased morbidity associated with this. We remain
unconvinced that such a "maximal" thymectomy should be considered the procedure of choice for all patients with myasthenia gravis.
Donald G. Mulder, M D Division of Cardiothoracic Surgery UCLA School of Medicine Center for the Health Sciences 10833 Le Conte Ave Los Angeles, C A 90024-1741
Intraoperative Photodynamic Therapy for Malignant Mesothelioma To the Editor: We read with interest the article by Watts and colleagues entitled "Giant benign mesothelioma" [l], and we would like to bring to your attention a new approach that is being investigated at our institution for the possible management of diffuse pleural malignant mesothelioma. This approach involves the preoperative delivery of a photosensitizer (dihematoporphyrin ether) and debulking of disease to 5 mm thickness, either by pleurectomy or extrapleural pneumonectomy, followed by intraoperative delivery of 630-nm light using an argon pump-dye laser. This therapy, known as photodynamic therapy, is based on the in vivo selective retention of sensitizer by malignant tissue and relatively superficial depth penetration of light wavelengths (5 to 7 mm), which may be useful in the treatment of surface malignancies (neoplasms of skin, bladder, bronchus, and esophagus) [2]. We recently treated a 58-year-old man with right-sided diffuse pleural mesothelioma by performing an extrapleural pneumonectomy 2 days after he received 2.0 mg/kg of dihematoporphyrin ether. After the diaphragm was replaced with dura mater, the only areas of gross residual disease included the lateral chest wall at the diaphragmatic sulcus, and these areas were debulked to 5 mm thickness or less. After hemostasis was obtained, seven sterile photodiodes were sewn to the chest cavity superiorly (I), inferiorly (2), medial, lateral, and posteriorly (1 each), and one photodiode was secured to the right ventricular epicardium. These photodiodes were then attached to a continuously integrating computerized photometer for instantaneous and cumulative recording of light power density and integrated energy density from the areas monitored by the photodiodes. The chest cavity was then filled with 0.02% intralipid for light scattering, and pleural illumination was accomplished with two specially instrumented laser fibers, one each from two lasers. Seven watts of continuous 630-nM light was used to deliver a total dose of 15 J/cm2to the chest cavity. The heart was treated to a total dose of 11J/cm2.After light delivery the photodiodes were removed, and the chest was closed without drainage. Total operative time was 8 hours, with 37 minutes of laser time. The patient was extubated the following morning. The only evidence of substantial chemical abnormality included a rise in the serum creatinine level from 90 to 140 Fmol/L (1.0 to 1.6 mg/dL) on the night of operation, which normalized with hydration over the next 48 hours, and a rise in the creatine kinase level from a baseline of 44 to 11,030 U/L 72 hours after photodynamic therapy. Myoglobin was absent from the urine (
