Radioiodine remnant ablation: current indications and dosing regimens

To review and comment on current indications for radioiodine remnant ablation (RRA) in patients with differentiated thyroid cancer.

The stratification of patients as potential candidates for RRA, the benefits and risks of RRA, and the optimal preparation and administered doses of iodine 131 for RRA are discussed.

When RRA for patients with low- and intermediate-risk differentiated thyroid cancer is being considered, the benefits-including survival, influence on morbidity and recurrence, and ease of monitoring-should be weighed against the potential risks. RRA should have limited use in many low-risk patients, particularly those with stage I disease who are young and have small primary tumors, no lymph node involvement, and no extranodal invasion. Measurement of serum thyroglobulin 6 to 8 weeks after thyroidectomy during levothyroxine suppression can be used for further stratification of risk in these patients. RRA should be used only selectively in low- to intermediate-risk patients and reserved primarily for older patients with large tumors, extensive lymph node involvement, and high-risk (tall cell, insular) subtypes of differentiated thyroid cancer. Most low-risk to intermediate-risk patients who do warrant RRA can be prepared with recombinant human thyroid-stimulating hormone and given the smallest dose possible (30 to 50 mCi of iodine 131) for successful remnant ablation. Single-photon emission computed tomography-computed tomographic imaging and dosimetry are new tools that can help in the management of many patients with thyroid cancer.

Although a large database study has shown a trend of increased use of RRA after thyroidectomy between 1990 and 2008 in the United States, recent studies and guidelines suggest a more limited use in patients with low-risk disease, which may change this trend.