Role of 131I in the treatment of well differentiated thyroid cancer.

(131)I is an integral component in postsurgical management of well-differentiated thyroid cancer (WDTC), which includes papillary and follicular types. (131)I is used postsurgically to either destroy remaining thyroid tissue (thyroid ablation) or to treat recurrence and metastases (radioiodine therapy). (131)I is no longer a routine diagnostic modality, but it is widely used for remnant ablation after thyroidectomy for WDTC > 1 cm, under conditions of thyroxine withdrawal. It is generally-though not unanimously-accepted that postsurgical radioiodine is the most powerful method by which to lengthen disease-free survival. (131)I cannot be used if the residual thyroid remnant is large; many surgeons therefore perform near-total or total thyroidectomy for all WDTC > 1 cm. Since 1997, radioiodine treatment has been performed in outpatient settings, where side effects are common, but mild and transient. Secondary screening is by physical exam, thyroglobulin measurements, and (131)I diagnostic whole-body scans. This is performed under conditions of thyrotropin stimulation, which is accomplished either by thyroxine withdrawal or administration of recombinant human thyrotropin. While most cancers are well treated with radioiodine, some advanced cancers may no longer take up radioiodine, rendering them resistant to treatment. For these cancers, redifferentiation therapy and molecular target-specific medicines hold future promise for improved treatment.