High-dose radiation and the emergence of thyroid nodular disease

High-dose radiation (in excess of 2500 rads or centiGray) to the head and neck area is reputedly infrequently associated with the emergence of thyroid nodular disease. Thirty-three patients who underwent high-dose radiation and who developed thyroid nodular disease have been described. Radiation was originally administered for hyperthyroidism in 11 patients, postmastectomy in five, oral cancer in three, Hodgkin's disease in three, facial hirsutism in three, hemangioma in three, cancer of the larynx in one, skin cancer in one, desmoid tumor of the neck in one, Ewing's tumor in one, and pituitary tumor in one. Treatment included radioiodine in 11, external radiation in 21, interstitial radiation in one, and combined radiation in one. Associated head and neck neoplasms included four parathyroid tumors, one osteogenic sarcoma of the maxilla, two basal cell cancers of the facial skin, and one parotid gland carcinoma. The study group consisted of five men and 26 women varying in age from 22 to 75 years, with a duration of latency of effect varying from 1.5 to 50 years. Thyroid disease consisted of 21 cancers, six adenomas, four colloid goiters, and two cases of thyroiditis resulting in four deaths caused by cancer, for a 20% mortality rate. Consideration of radiation beam behavior showed that isodose curve, penumbra effect, back scatter, and special field resulted in the thyroid gland receiving a low dose, namely under 2500 rads. Clinical factors such as an overlooked goiter, coincidental carcinoma, error in presumption of dose, and second primary malignancy were also considerations. True biologic radiation oncogenesis may have been seen in our radioiodine-treated group with hyperthyroidism as well as the group with Hodgkin's disease who underwent mantle irradiation. It is apparent that for whatever reason and by whatever means and by whatever mechanism, high-dose radiation to the head and neck area can result in significant thyroid disease, and patients undergoing such radiation should be followed with this in mind and considered for thyroid feeding on a prophylactic basis.