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

The use of radioactive iodine ((131)I) 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 (131)I and new discoveries concerning the biology of iodine handling by thyroid cells. The therapeutic administration of (131)I for thyroid remnant ablation and for metastases requires an appreciation of iodine clearance kinetics, of factors that can alter the occupancy time of (131)I within lesions, and of the role of thyroid-stimulating hormone in stimulating the sodium-iodide symporter. The potential complications and adverse events associated with (131)I are discussed. (131)I 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.