0360.3016/92 $5.00 + .Oil Copyright 0 1992 Pergamon Press Ltd.
Im. J. Radiulron Oncolo~.v Biol Phys.. Vol. 22, pp. 1155-l 156 Printed in the U.S.A. All rights reserved.
??Editorial
UNNECESSARY
MORBIDITY FOLLOWING IRRADIATION OF LATERALIZED HEAD AND NECK CARCINOMA C. C. WANG, M.D.
Department
of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02 114
The limited radiosensitivity of various cellular components of pleomorphic adenomas has allowed surgical extirpation to be the conventional curative procedure. Radiation therapy remains primarily adjuvant in nature and is commonly used postoperatively in patients with positive resection margins, deep lobe involvement, tumor spillage, or tumor adherence to facial nerve or with multiple tumor recurrences. Because of the indolent and chronic nature of the disease, pleomorphic adenomas are rarely lethal, and most patients survive with the tumor for a long duration of time. Treatment of this benign tumor with either surgery or radiation therapy must be tempered with conservatism. Aggressive irradiation with excessively high dose is illadvised and does a disservice to patients with this disease. The article by Barton et al. (1) presented the efficacy of radiation therapy in the prevention of recurrence of pleomorphic adenomas. Unfortunately, the complications after radiation therapy for a benign lesion were unusually high and, at times, considered prohibitive, that is 2% radionecrosis and 2.7% facial nerve palsy. These undesirable radiation sequelae are lasting and could be the results of poor treatment planning and/or antiquated technique and may be avoidable with state of the art radiation therapy. For radiation therapy of lateralized lesions of the head and neck, including parotid pleomorphic adenoma and carcinomas, tumors of the temporal bone, faucial pillars and tonsils, retromolar trigone, alveolar ridge, etc., avoidance of irradiation to the contralateral nontarget structures is good clinical practice. This is often accomplished by employing ipsilateral oblique wedge pair (2, 3, 4) or unilateral appositional photon or electron techniques. Unfortunately, the use of any one of these treatment modalities alone is not optimum and may result in unnecessary irradiation morbidity.
In the ipsilateral oblique wedge pair treatment of parotid lesions (e.g., using cobalt 60 or 4 MV photons to a dose of 55-65 Gy), there is a “hot spot” of 8-10% at the entrance of the portal as compared to the isocenter over the tumor volume. This results in an unintentional increase in the doses to the adjacent temporal bone or mandible to 60-72 Gy. Due to increased fraction size at the “hot spot,” the biologic dose is even higher, and occasionally osteoradionecrosis may ensue. Therefore, it is of the utmost importance that the tolerance of various important anatomic structures lying within the so-called morbid triangle (i.e., the spinal cord, temporal bone, and mandible) not be exceeded; otherwise serious complications, including radiation myelitis, osteoradionecrosis of the temporal bone, or mandible, may occur. While the latter may be remedied by surgery, the former two often cannot. The unnecessary irradiation morbidity following treatment of lateralized lesions can be prevented by using a combination of anterior-posterior and/or superior-inferior lateral oblique wedge pair photons intermixed with en face electron beam and/or supplemented with small photon doses, that is, 15-20 Gy via parallel opposed lateral portals route. For pleomorphic adenomas or carcinomas with positive margins, a dose of 55-60 Gy in 5 to 6 weeks should suffice as a postoperative procedure. For unresectable carcinomas, a much higher dose is needed, such as 65-70 Gy in 6 to 7 weeks. Needless-m-say, all portals should be treated daily with fraction size not to exceed 2 Gy. A composite isodose of various treatment plans toward the projected final dose is required to’detect excessive “hot spots” and to ensure dose homogeneity. This, in turn, will deliver maximum dose to the target volume with tolerable doses to various anatomic sites in the “morbid triangle,” thus resulting in improved local tumor control and minimum radiation therapy morbidity.
Reprint requests to: C. C. Wang, M.D.
Accepted for publication
1155
20 December 199 1.
1156
1. J. Radiation Oncology 0 Biology 0 Physics
Volume 22, Number 5, 1992
REFERENCES 1. Barton, J.; Selvin, N. J.; Cleaves, E. N. Radiotherapy for pleomorphic adenoma of parotid gland. Int. J. Radiat. Oncol. Biol. Phys. (In press). 2. Montague, E. D. Tumors involving the middle ear and temporal bone. In: Fletcher G. H., ed. 3rd ed. Textbook of radiotherapy. Philadelphia, PA: Lea & Febiger; 1980: 398400.
3. Simpson, R. D. Cancer of the salivary gland. In: Perez C. A.; Brady L. W., eds. Principles and practice of radiation oncology. Philadelphia, PA: Lippincott Co.; 1987: 5 17-5 18. 4. Boutin, N. S. The temporal bone, external auditory canal, middle ear, paragangliomata. Moss, W. T.; Cox, J. D. 6th ed. Radiation oncology. St. Louis, MO: C. V. Mosby Co; 1989: 188-189.
Im. J. Radiulron Oncolo~.v Biol Phys.. Vol. 22, pp. 1155-l 156 Printed in the U.S.A. All rights reserved.
??Editorial
UNNECESSARY
MORBIDITY FOLLOWING IRRADIATION OF LATERALIZED HEAD AND NECK CARCINOMA C. C. WANG, M.D.
Department
of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02 114
The limited radiosensitivity of various cellular components of pleomorphic adenomas has allowed surgical extirpation to be the conventional curative procedure. Radiation therapy remains primarily adjuvant in nature and is commonly used postoperatively in patients with positive resection margins, deep lobe involvement, tumor spillage, or tumor adherence to facial nerve or with multiple tumor recurrences. Because of the indolent and chronic nature of the disease, pleomorphic adenomas are rarely lethal, and most patients survive with the tumor for a long duration of time. Treatment of this benign tumor with either surgery or radiation therapy must be tempered with conservatism. Aggressive irradiation with excessively high dose is illadvised and does a disservice to patients with this disease. The article by Barton et al. (1) presented the efficacy of radiation therapy in the prevention of recurrence of pleomorphic adenomas. Unfortunately, the complications after radiation therapy for a benign lesion were unusually high and, at times, considered prohibitive, that is 2% radionecrosis and 2.7% facial nerve palsy. These undesirable radiation sequelae are lasting and could be the results of poor treatment planning and/or antiquated technique and may be avoidable with state of the art radiation therapy. For radiation therapy of lateralized lesions of the head and neck, including parotid pleomorphic adenoma and carcinomas, tumors of the temporal bone, faucial pillars and tonsils, retromolar trigone, alveolar ridge, etc., avoidance of irradiation to the contralateral nontarget structures is good clinical practice. This is often accomplished by employing ipsilateral oblique wedge pair (2, 3, 4) or unilateral appositional photon or electron techniques. Unfortunately, the use of any one of these treatment modalities alone is not optimum and may result in unnecessary irradiation morbidity.
In the ipsilateral oblique wedge pair treatment of parotid lesions (e.g., using cobalt 60 or 4 MV photons to a dose of 55-65 Gy), there is a “hot spot” of 8-10% at the entrance of the portal as compared to the isocenter over the tumor volume. This results in an unintentional increase in the doses to the adjacent temporal bone or mandible to 60-72 Gy. Due to increased fraction size at the “hot spot,” the biologic dose is even higher, and occasionally osteoradionecrosis may ensue. Therefore, it is of the utmost importance that the tolerance of various important anatomic structures lying within the so-called morbid triangle (i.e., the spinal cord, temporal bone, and mandible) not be exceeded; otherwise serious complications, including radiation myelitis, osteoradionecrosis of the temporal bone, or mandible, may occur. While the latter may be remedied by surgery, the former two often cannot. The unnecessary irradiation morbidity following treatment of lateralized lesions can be prevented by using a combination of anterior-posterior and/or superior-inferior lateral oblique wedge pair photons intermixed with en face electron beam and/or supplemented with small photon doses, that is, 15-20 Gy via parallel opposed lateral portals route. For pleomorphic adenomas or carcinomas with positive margins, a dose of 55-60 Gy in 5 to 6 weeks should suffice as a postoperative procedure. For unresectable carcinomas, a much higher dose is needed, such as 65-70 Gy in 6 to 7 weeks. Needless-m-say, all portals should be treated daily with fraction size not to exceed 2 Gy. A composite isodose of various treatment plans toward the projected final dose is required to’detect excessive “hot spots” and to ensure dose homogeneity. This, in turn, will deliver maximum dose to the target volume with tolerable doses to various anatomic sites in the “morbid triangle,” thus resulting in improved local tumor control and minimum radiation therapy morbidity.
Reprint requests to: C. C. Wang, M.D.
Accepted for publication
1155
20 December 199 1.
1156
1. J. Radiation Oncology 0 Biology 0 Physics
Volume 22, Number 5, 1992
REFERENCES 1. Barton, J.; Selvin, N. J.; Cleaves, E. N. Radiotherapy for pleomorphic adenoma of parotid gland. Int. J. Radiat. Oncol. Biol. Phys. (In press). 2. Montague, E. D. Tumors involving the middle ear and temporal bone. In: Fletcher G. H., ed. 3rd ed. Textbook of radiotherapy. Philadelphia, PA: Lea & Febiger; 1980: 398400.
3. Simpson, R. D. Cancer of the salivary gland. In: Perez C. A.; Brady L. W., eds. Principles and practice of radiation oncology. Philadelphia, PA: Lippincott Co.; 1987: 5 17-5 18. 4. Boutin, N. S. The temporal bone, external auditory canal, middle ear, paragangliomata. Moss, W. T.; Cox, J. D. 6th ed. Radiation oncology. St. Louis, MO: C. V. Mosby Co; 1989: 188-189.
