Long-term efficacy of modified-release recombinant human thyrotropin augmented radioiodine therapy for benign multinodular goiter: results from a multicenter, international, randomized, placebo-controlled, dose-selection study

Background: Enhanced reduction of multinodular goiter (MNG) can be achieved by stimulation with recombinant human thyrotropin (rhTSH) before radioiodine ( 131I) therapy. The objective was to compare the long-term efficacy and safety of two low doses of modified release rhTSH (MRrhTSH) in combination with 131I therapy. Methods: In this phase II, single-blinded, placebo-controlled study, 95 patients (57.2±9.6 years old, 85% women, 83% Caucasians) with MNG (median size 96.0mL; range 31.9-242.2mL) were randomized to receive placebo (n=32), 0.01mg MRrhTSH (n=30), or 0.03mg MRrhTSH (n=33) 24 hours before a calculated 131I activity. Thyroid volume (TV) and smallest cross-sectional area of trachea (SCAT) were measured (by computed tomography scan) at baseline, six months, and 36 months. Thyroid function and quality of life (QoL) was evaluated at three-month and yearly intervals respectively. Results: At six months, TV reduction was enhanced in the 0.03mg MRrhTSH group (32.9% vs. 23.1% in the placebo group; p=0.03) but not in the 0.01mg MRrhTSH group. At 36 months, the mean percent TV reduction from baseline was 44±12.7% (SD) in the placebo group, 41±21.0% in the 0.01mg MRrhTSH group, and 53±18.6% in the 0.03mg MRrhTSH group, with no statistically significant differences among the groups, p=0.105. In the 0.03mg MRrhTSH group, the subset of patients with basal 131I uptake 131I, enhanced MNG reduction could not be demonstrated with MRrhTSH doses ≤0.03mg, indicating that the lower threshold for efficacy is around this level.