Recombinant Human Thyrotropin Versus Thyroid Hormone Withdrawal for Radioactive Iodine Therapy in Metastatic Differentiated Thyroid Cancer: A Multicenter Retrospective Study.

This study compared clinical and safety outcomes of radioactive iodine therapies administered after thyroid hormone withdrawal (THW) versus recombinant human thyrotropin (rhTSH) in patients with differentiated thyroid cancer and distant metastases, using both patient- and therapy-based analyses. Methods: Patient-based analyses included 352 patients classified into the THW-only (n = 259), rhTSH-only (n = 40), or mixed (n = 53) groups, whereas therapy-based analyses included 564 radioactive iodine therapies administered after THW (n = 459) or rhTSH (n = 105). Overall survival and disease-specific survival were assessed at the patient level, whereas imaging-based response, change in thyroglobulin after therapy (biochemical response), and laboratory-based safety outcomes were evaluated at the therapy level. Results: Overall survival and disease-specific survival did not differ significantly among the 3 patient groups (all P > 0.25). Imaging- and biochemical-response outcomes also were comparable between groups who received RAI therapy after THW and rhTSH (both P > 0.05), and the preparation method was not significantly associated with either response outcome. In contrast, liver function abnormalities and the occurrence of at least 1 prespecified laboratory-based safety outcome were significantly more frequent after THW (both P < 0.001). Conclusion: rhTSH and THW were associated with comparable survival and treatment responses in patients with differentiated thyroid cancer with distant metastases, whereas laboratory-based safety outcomes were more frequent after THW preparation. These findings strengthen multicenter real-world evidence supporting rhTSH as an alternative to THW for select patients, particularly when minimizing prolonged hypothyroidism is important for individualized treatment planning.