Head and neck radiation carcinogenesis: epidemiologic evidence.

This article provides an overview of the long-term carcinogenic effects of medical radiation exposure to the head and neck and focuses on studies that allow risk quantification. The thyroid gland in children is extremely sensitive to the tumorigenic effects of external radiation for many years after exposure. Risk of thyroid cancer decreases with increasing age at exposure, with little risk, if any, apparent among persons exposed as adults. Large risks of neural tumors have been reported after moderate- and high-dose radiotherapy in childhood; however, the magnitude of the risk at low doses and for adult exposures is unclear. Data on salivary gland tumors are limited but tend to support an association with radiation exposure. In contrast, the pituitary gland appears to be relatively resistant to the tumorigenic effects of radiation. Several cohort studies have reported an increased risk of hyperparathyroidism among irradiated populations. In summary, radiation exposure to the head and neck can result in tumors of the thyroid, salivary, and parathyroid glands, as well as the brain and central nervous system.