Long-Term Outcomes of Patients with Papillary Thyroid Cancer Undergoing Remnant Ablation with 30 milliCuries Radioiodine

Background: The study considered the long-term outcome of patients with papillary thyroid carcinoma treated with 30 mCi radioiodine. Objective: The aims of this study were to define and compare the remission rates of papillary thyroid carcinoma ablated with 30 mCi 131 I prepared by either thyroid hormone withdrawal (THW) or recombinant human thyrotropin (rhTSH; Thyrogen ® ), and to identify variables predictive of a favorable prognosis. Method: An observational study was conducted at an academic medical center and a comparative summary of six studies is presented. Three hundred and seventy patients (THW group, n = 203; rhTSH group, n = 167) were recruited from a prospectively managed registry. The mean follow-up was 9.3 years (range 5.1–15.8 years) in the THW group and 7.1 years (range 5.0–9.7 years) in the rhTSH group. The primary endpoint was the long-term remission rates (no evidence of disease) in the THW group compared with the rhTH group. Results: The response at 12–18 months after 30 mCi remnant ablation was excellent in 79.3% and 76.0% of patients in the THW group and the rhTSH group, respectively ( p > 0.05). The long-term remission rates also did not significantly differ between both groups at 95.6% and 97.0%. Although the surveillance period for the THW group exceeded that of the rhTSH group, no significant difference in recurrence-free survival was discerned by the Kaplan–Meier curves. In a multivariate analysis, an excellent response to therapy at 12–18 months correlated significantly with long-term remission rates in the THW group ( p = 0.031, odds ratio [OR] = 2.6 [confidence interval (CI) 1.1–6.0]), the rhTSH group ( p = 0.03, OR = 5.3 [CI 1.2–23.8]), and the pooled groups ( p = 0.001, OR = 3.43 [CI 1.63–7.2]). The pre-ablation thyroglobulin level significantly correlated with remission rates only in the THW group ( p = 0.035, OR = 5.5 [CI 1.1–27.1]). Conclusions: The response to remnant ablation with 30 mCi radioiodine is often excellent, and the long-term remission rates can be expected to be high, independent of the method of delivery (i.e., THW or rhTSH).