The evolving role of ¹³¹I for the treatment of differentiated thyroid carcinoma

The use of radioactive iodine (¹³¹I) for the treatment of thyroid carcinoma has changed over the past 50 y. These changes are based on increasing awareness of the biophysical properties of ¹³¹I and new discoveries concerning the biology of iodine handling by thyroid cells. The therapeutic administration of ¹³¹I for thyroid remnant ablation and for metastases requires an appreciation of iodine clearance kinetics, of factors that can alter the occupancy time of ¹³¹I within lesions, and of the role of thyroid-stimulating hormone in stimulating the sodium-iodide symporter. The potential complications and adverse events associated with ¹³¹I are discussed. ¹³¹I will continue to be a major weapon in the fight against metastatic thyroid carcinoma. Its future role will be modified by expanding knowledge of its relative risks and benefits.