Neoplasms induced by megavoltage radiation in the head and neck region

Radiation-induced cancer, although fortunately a rare complication of radiotherapy, is nonetheless observed occasionally even after megavoltage radiation has been used. Over a 22-year period at the Curie Institute, four patients were found to have malignant neoplasms within the fields of megavoltage treatment given for various cancers of the head and neck region. Three of the neoplasms were sarcomas, two osteogenic and one fibrosarcoma, and the other tumor was a sarcomatoid epithelioma. The latent period ranged from 3 1/2-15 years. Although the evidence is strong that the neoplasms were causally related to the precedent irradiation, it is acknowledged that rare examples of the "double primary" phenomenon exist, even separated by five or more years, and that only one such instance would induce a large error in the estimated frequency of postirradiation neoplasms. Because clinical estimates after megavoltage irradiation are usually compounded by an association with a relatively high total absorbed dose, the issue of the incidence of postirradiation neoplasms as a function of the type of external beam (orthovoltage vs. megavoltage) may require resolution by experimental means. Another rare sequela of radiotherapy is injury to a peripheral nerve. One of the four patients with a second neoplasm after radiation also developed left hypoglossal nerve palsy 2 1/2 years post-therapy, and left optic nerve atrophy seven years postradiation treatment of a squamous cell carcinoma of the ethmoid and maxillary sinuses. The 51-year-old patient had received a tumor dose of 6800 rads (2043 rets).