THE USE of radioactive iodine (I131) has become an established procedure in treating certain types of metastatic carcinoma of thyroid origin. The possibility exists that radiations from I131 may produce a malignant tumor in adjacent tissues of the thyroid itself. Quimby and Werner1 collected cases of hyperthyroidism treated by regional x-ray therapy and reported that the incidence of carcinoma of the thyroid and larynx in these cases was no higher than in the general population. Gorbman,2 studying the effects of I131 on the neck organs of experimental animals, concluded that when doses ranging upward from 50,000 rep had been delivered, abnormal changes and tumors were produced in the thyroid and trachea. Maloof * could not produce thyroid carcinoma in animals by administering large doses of I131.
One case has been reported (Trunnell3) in which a patient with thyroid cancer was discovered to have a