MON-LB87 Recombinant Human TSH vs Thyroid Hormone Withdrawal Preparation for Radioiodine Ablation in Pediatric Differentiated Thyroid Cancer

Introduction: Recombinant human TSH (rhTSH) is commonly used to prepare patients with differentiated thyroid cancer (DTC) for radioiodine (I-131) ablation after total thyroidectomy (TT). In adults, rhTSH is associated with equivalent oncologic efficacy and improved health-related quality of life in comparison to thyroid hormone withdrawal (THW). In this study, we aimed to measure disease-free survival after rhTSH stimulation vs. THW in pediatric patients with DTC. Methods: A prospective database was analyzed for pediatric patients under the age of 21 with DTC who underwent TT and I-131 ablation with rhTSH preparation at a single tertiary institution from 2012 through 2018. These patients were compared against historical controls prepared with THW. Tumor stage, I-131 treatment details, disease-free survival, structural recurrence, biochemical recurrence (defined as serum Tg > 2 at one year), and postoperative serum TSH, thyroglobulin (Tg) and Tg antibody levels were recorded. The log-rank test was used to compare groups, and time to recurrence was estimated by Kaplan-Meier analysis. Results: Seventeen patients who received rhTSH (mean age, 16.6±3.2 [SD] years) were compared to 28 historical controls prepared with THW. No differences were observed in RAI dose (mean 2.3±0.7 mCi/kg), tumor stage, or follow-up time (median [IQR] 2.6 [1.1-3.1] years) between groups. The THW group exhibited a nonsignificantly greater recurrence rate (14 [50%], 7 with biochemical recurrence and 7 with structural recurrence) than the rhTSH group (three [18%], 2 with biochemical recurrence and 1 with structural recurrence, p=0.2). A trend toward improved disease-free survival was identified in those treated with rhTSH compared to THW. Conclusion: In this cohort of pediatric patients with DTC, we observed a trend toward improved disease-free survival among those prepared with rhTSH compared to historical controls prepared with THW. Long-term follow up is needed to better characterize outcomes associated with rhTSH stimulation prior to I-131 ablation in the pediatric population.