I -131 Treatment

Estimation of thyroid doses for patients treated with I-131 for hyperthyroidism

The REB conducts a study in cohort of 35,573 patients treated for hyperthyroidism. A major purpose of the study is to determine whether post-therapeutic leukemia or other malignancies occurred more often in patients receiving Iodine-131 treatment for hyperthyroidism than in patients treated by antithyroid drugs or surgery. To reconstruct the organ doses due to oral administration of Iiodine-131, REB dosimetrists have developed a new biokinetic model for iodine to be applied for hyperthyroid patients. Parameters of model were obtained from results of measurements of iodine in blood, urine, and thyroid following treatments for thyrotoxicosis for 3138 patients. For these patients with available measured data, the individual organ doses have been calculated based on the administered activity of Iodine-131 and the predictions of the amounts of iodide and protein-bound-iodine present in each organ and tissue as well as the biological behavior of iodine in the body. Estimation of organ doses to all cohort members is in progress.