Radioiodine ablation with 1,850 MBq in association with rhTSH in patients with differentiated thyroid cancer Alberto S. TresoldiLaura F. SburlatiMarcello RodariMink Schinkelshoek • Michela PerrinoSimone De LeoLaura MontefuscoPaolo ColomboMaura Arosio • Andrea Gerardo Antonio LaniaLaura FugazzolaArturo Chiti

Purpose The aim of this study was to evaluate the efficacy of post-operative radioiodine ablation with 1,850 MBq after recombinant human thyrotropin (rhTSH) administration in patients with differentiated thyroid carcinoma (DTC). We also aimed to assess the prognostic role of several patient features on the outcome of ablation. Methods We retrospectively analyzed data from a total of 125 patients with DTC who underwent post-operative radioiodine ablation with 1,850 MBq of 131 I after preparation with rhTSH. One injection of 0.9 mg rhTSH was administered on each of two consecutive days; 131 I therapy was delivered 24 h after the last injection, followed by a post-therapy whole-body scan. Successful ablation was assessed 6‐12 months later and defined as an rhTSHstimulated serum thyroglobulin (Tg) level B1.0 ng/ml and a normal neck ultrasound. Results Patients were stratified according to the American Thyroid Association (ATA) Management Guidelines for Differentiated Thyroid Cancer. Successful ablation was achieved in 82.4 % of patients, with an ablation rate of 95.1 % in low-risk patients and 76.2 % in intermediate-risk patients. Analyzing the correlation between ablation outcome and patient characteristics, we found a statistically significant association between failure to ablate and class of risk based on ATA guidelines (p = 0.025) and a stimulated Tg value at ablation of above 5 ng/ml (p \ 0.001). Conclusion The use of 1,850 MBq post-operative radioiodine thyroid remnant ablation in association with rhTSH is effective for low- and intermediate-risk patients. Moreover, in our study, we found a statistical correlation between failure to ablate and class of risk based on ATA guidelines for DTC and a stimulated Tg value at ablation.