Introduction Antithyroid drugs (ATDs) are commonly administered prior to radioactive iodine therapy (RAIT) for Graves’ disease (GD), but their impact on RAIT efficacy remains unclear, largely due to insufficient adjustment for confounding factors in previous studies.Methods This retrospective study evaluated the impact of ATD treatment duration on RAIT outcomes using propensity score matching (PSM) to control for key covariates. Eighty patients with GD who underwent RAIT between 2015 and 2023 were classified into short-term (S group, <3 months) and long-term (L group, ≥3 months) ATD treatment cohorts (pre-PSM cohorts). After matching for age, thyroid weight, and 131I absorbed dose, 48 patients (24 per group) were enrolled in the PSM. Treatment efficacy was assessed using thyroid weight and percent thyroid weight reduction at 1 year post-RAIT (TW-1y and %TW-1y, respectively).Results The S group demonstrated significantly lower TW-1y (4.9 ± 2.6 g vs. 7.7 ± 5.1 g, p = 0.033) and greater %TW-1y (78.6 ± 8.3% vs. 68.0 ± 14.2%, p = 0.005) than the L group, despite higher TRAb and TSAb levels, which are typically associated with reduced treatment response. Standardized mean difference analysis confirmed adequate covariate balance, and doubly robust sensitivity analysis supported the reliability of these findings.Conclusion These results suggest that prolonged ATD administration before RAIT is associated with reduced therapeutic efficacy, providing stronger evidence than prior observational reports.
Tachibana et al. (Thu,) studied this question.