Incidence of thyroid carcinoma in patients who had diagnostic iodine-131 tests during childhood and adolescence

To determine the carcinogenic effects of diagnostic amounts of radioactive iodine-131 on the infantile thyroid gland a multi-center retrospective cohort study was conducted which included data of 4973 subjects who had either been referred to diagnostic iodine-131 uptake tests (2262 subjects) or had had a diagnostic procedure of the thyroid without 131-iodine (2711 subjects) until the age of 18 years. Follow-up examinations of 35 percent of the subjects in the iodine-131 group and 41 percent of the subjects in the control group took place after a mean time period of 20 years after the first examination. Dosimetry of the thyroid burden of iodine-131 was carried out according to ICRP 53. The median of the thyroid organ dose was 1012 mGy. The report compares prevalences or incidences of thyroid disorders resp. occurring in both groups and gives a stratified analysis of primary diagnosis, age at exposure, and organ dose. A total number of five carcinomas of the thyroid was found. In the radioiodine group two carcinomas were assessed in a period of 16500 person-years. The control group yielded three carcinomas over 21000 person-years (Relative rate: 0,89, 95% confidence interval: 0,14-5,13). (orig.)