Long-term outcome and prognostic factors of single-dose Radioiodine Therapy in patients with Graves' disease.

BACKGROUND/PURPOSE: Few studies exist investigating the effectiveness of radioiodine (RAI) therapy for hyperthyroidism patients in Asia. We herein investigated the real-world efficacy of single-dose RAI therapy in Taiwanese patients with Graves' disease (GD).

METHODS: This is a retrospective study of 243 patients with GD recorded between 1989 and 2016 in a tertiary referral hospital. Eu- or hypothyroid after RAI therapy were defined as the successful group. Kaplan-Meier curve and cox-regression model were used for analysis of prognostic factors.

RESULTS: Of the 243 patients, 187 were females, with mean age of 46.9 ± 13.6 years. Most patients (63.8%) did not choose RAI as the first-line therapy. The median dose was 7 mCi, with a mean follow-up period of 107.1 ± 82.8 months. The overall success rate was 70.9%. Univariate analysis revealed calculated- or fixed-dose (P = 0.015), goiter size (P < 0.001), and RAI dose (P = 0.022) were the factors affecting RAI effectiveness, multivariate analysis indicated goiter size was the independent factor. Patients with grade 0-2 goiter had a higher success rate than patients with grade 3 goiter (HR = 2.1, 95%CI = 1.34-3.27, P = 0.001), although the former were treated with lower RAI dose than the latter (7.8 ± 3.2 mCi vs 8.8 ± 3.3 mCi, P = 0.049). However, if the grade 3 goiters became smaller within 3 months of therapy, the success rate was not inferior to grade 0-2 goiter.

CONCLUSIONS: In Taiwan, RAI therapy for GD patients reached an overall success rate of 70.9%, with a median dose of 7 mCi. This study identified patients with grade 3 goiter need a more aggressive RAI regimen.