Influence of prior carbimazole on the outcome of radioiodine therapy in pediatric and adolescent Graves' disease.

Objective Of The Study: Therapeutic options for pediatric Graves' disease (PGD) include antithyroid drug therapy (ATD) as the first line and radioiodine (I-131) therapy as the second line of treatment. To date, controversies persist regarding the true effect of prior ATD in the outcome of I-131 therapy in PGD. This study evaluated the effect of prior carbimazole treatment on the outcome of I-131 therapy in PGD.

Methods: This is a retrospective study covering the years 1995-2012, with a median follow-up of 75 months. Records of 114 children (84 girls and 30 boys, age range: 5-20 years, mean 24-h radioiodine uptake, 58%) who had clinically and biochemically proven Graves' disease irrespective of prior ATD therapy were included. All patients were treated with fixed doses of 5 mCi (185 MBq) I-131 for Graves' disease; 74 had undergone prior carbimazole treatment (group 1) and 40 were drug naive (group 2). The endpoint of follow-up was stable euthyroid or hypothyroid in patients. The effect of prior carbimazole treatment on the outcome of I-131 therapy in PGD patients was evaluated. The success of radioiodine therapy was defined as the cure of hyperthyroidism. Variables were analyzed to identify the potential predictive factors for euthyroidism/hypothyroidism after treatment.

Results: The cure rate was 70% in group 1 and 83% in group 2 with a single dose of radioiodine (P=0.299). The success rate achieved at the end of 1-year follow-up in group 1 and group 2 was 81 and 87%, respectively (P=0.401). No independent predictor was associated with success or failure of treatment. At the median follow-up of 75 months (range: 12-216 months), 76% of patients were hypothyroid on replacement doses of levothyroxine and 24% still continued to be euthyroid.

Conclusion: Prior carbimazole treatment does not alter the outcome of radioiodine therapy in PGD.