Recombinant Human TSH–Assisted Radioactive Iodine Remnant Ablation Achieves Short-Term Clinical Recurrence Rates Similar to Those of Traditional Thyroid Hormone Withdrawal

Abstract

Recent studies have confirmed that radioactive iodine therapy after recombinant human TSH (rhTSH) stimulation effectively ablates the normal thyroid remnant. However, no published study has determined the effectiveness of rhTSH preparations on the important endpoint of disease recurrence. Methods: Disease recurrence was retrospectively assessed a median of 2.5 y after radioiodine remnant ablation (RRA) in 394 consecutive thyroid cancer patients (93% papillary, 71% female, 47 ± 15 y old [mean ± SD], median ¹³¹I dose of 3,996 MBq [108 mCi]). Results: Similar rates of clinically evident disease recurrence (4% rhTSH vs. 7% thyroid hormone withdrawal [THW], P = not statistically significant) and residual thyroid bed uptake without other evidence of persistent disease (4% rhTSH vs. 7% THW, P = not statistically significant) were seen in the 320 patients undergoing rhTSH-assisted RRA and the 74 patients prepared for RRA by THW. When the definition of no clinical evidence of disease included a suppressed thyroglobulin level of less than 1 ng/mL and a stimulated thyroglobulin level of less than 2 ng/mL, rhTSH-assisted RRA was associated with significantly higher rates of no clinical evidence of disease (74% rhTSH vs. 55% THW, P = 0.02) and significantly lower rates of persistent disease (19% rhTSH vs. 32% THW, P = 0.02) than was RRA after THW. Patients selected for rhTSH-assisted RRA were older (48 ± 15 vs. 44 ± 15 y, P = 0.03) and received a slightly higher administered activity of ¹³¹I (median, 4,033 MBq [109 mCi] vs. 3,811 MBq [103 mCi], P = 0.01) but did not differ with respect to sex, histology, disease stage, or mean time to recurrence (19 ± 9 mo for rhTSH vs. 20 ± 16 mo for THW). Conclusion: rhTSH-assisted RRA is associated with rates of clinically evident disease recurrence and persistent uptake in the thyroid bed that are similar to those for traditional THW.