Follow-Up of Low-Risk Differentiated Thyroid Cancer Patients Who Underwent Radioiodine Ablation of Postsurgical Thyroid Remnants after Either Recombinant Human Thyrotropin or Thyroid Hormone Withdrawal

Background: We previously demonstrated comparable thyroid remnant ablation rates in postoperative low-risk thyroid cancer patients prepared for administration of 3.7GBq (131)I (100 mCi) after recombinant human (rh) TSH during T(4) (L-T4) therapy vs. withholding L-T4 (euthyroid vs. hypothyroid groups). We now compared the outcomes of these patients 3.7 yr later. Patients and Methods: Fifty-one of the 63 original patients (28 euthyroid, 23 hypothyroid) participated. Forty-eight received rhTSH and serum thyroglobulin (Tg) sampling. A (131)I whole-body scan was performed in 43 patients, and successful ablation was defined by criteria from the previous study. Based on the criterion of uptake less than 0.1% in thyroid bed, 100% (43 of 43) remained ablated. When no visible uptake instead was used, five patients (four euthyroid, one hypothyroid) had minimal visible activity. When the TSH-stimulated Tg criterion was used, only two of 45 (one euthyroid, one hypothyroid) had a stimulated Tg level greater than 2 ng/ml. Results: No patient in either group died, and no patient declared disease free had sustained tumor recurrence. Nine (four euthyroid, five hypothyroid) had received additional (131)I between the original and current studies due to detectable Tg or imaging evidence of disease; with follow-up, all now had a negative rhTSH-stimulated whole-body scan and seven (three euthyroid, four hypothyroid) had a stimulated serum Tg less than 2 ng/ml. Conclusions: In conclusion, after a median 3.7 yr, low-risk thyroid cancer patients prepared for postoperative remnant ablation either with rhTSH or after L-T4 withdrawal were confirmed to have had their thyroid remnants ablated and to have comparable rates of tumor recurrence and persistence. (J Clin Endocrinol Metab 94: 4171-4179, 2009)