Outcomes of radioactive iodine therapy with fixed-activity regimen in pediatric Graves' disease.

OBJECTIVE: To evaluate the success rates of radioactive iodine therapy (RAIT) with fixed activity of 10mCi and 15mCi in pediatric patients with Graves' disease (GD). SUBJECTS AND METHODS: dose of RAIT by fixed activity regimen, either 10mCi or 15mCi. The rates of successful therapy, defined as the induction of hypothyroidism within six months after RAIT, were compared between the two RAIT dosage groups. We also evaluated factors associated with the successful RAIT and median duration for achieving hypothyroidism between the two groups. RESULTS: Eighty-seven patients (86.2% females, mean (±standard deviation [SD]) age 14.7±2.5 years, 44.8% received 10mCi radioiodine) were included in the analysis. Patients who received 10mCi radioiodine exhibited a younger age at the GD diagnosis (P=0.038), younger age at the RAIT (P<0.001), and smaller thyroid size (P<0.001). The success rates of 10- vs 15mCi radioiodine were not significantly different (76.9% vs 64.6%, P=0.211). There was also no significant difference in the median duration to achieve hypothyroidism in 10- vs 15mCi groups (4.6 vs 5.1 months, P=0.306). Discontinuation of antithyroid drug (ATD) for more than three days prior to RAIT was the only independent factor for successful RAIT (adjusted odds ratio [OR] 3.67, P=0.015). CONCLUSION: Radioactive iodine therapy with fixed-activity regimen showed high success rates in pediatric patients with GD. Antithyroid drug withdrawal for more than three days prior to RAIT was recommended for the optimal therapeutic outcomes.