Radioiodine Treatment of Pediatric Graves’ disease: A Multicenter Review

Background: Hyperthyroidism in children is most commonly due to Graves’ Disease. First line treatment typically consists of anti-thyroid medications followed by either thyroidectomy or radioiodine (I-131) therapy in those children not achieving remission with medication alone. There is currently no consensus on optimal dosing of I-131 for the treatment of Graves’ Disease in children. The purpose of this study was to review the experience with I-131 therapy of Graves’ disease guided by ultrasound assessment of thyroid size in several dedicated pediatric hospitals.

Methods: This was a multicenter retrospective review of clinically collected data. Investigators at four dedicated pediatric hospitals collected data on pediatric patients (<21 years old) who had undergone both a thyroid ultrasound and I-131 therapy for Graves’ disease between 2009 and 2018. Data collected included: patient weight, thyroid lobe (right and left) volumes (in mL), pre-therapy 24-hour I-123 uptake, I-131 dose administered, and thyroid outcome (hyperthyroid, euthyroid, hypothyroid) at 6 and 12 months. Mann Whitney U test was used to compare groups.

Results: 65 patients were included, 53 female and 12 male. Median age was 15.5 years (range: 7-20 years). Patient weight was available for 49 patients (median 60.2 kg). Outcomes were available at either 6 or 12 months post-I-131 therapy in all included patients. At last assessment, 6 patients (9.2%) remained hyperthyroid, 10 were euthyroid and 49 were hypothyroid. For the entire population, median thyroid volume by ultrasound prior to therapy was 22.3 mL (min 7.5, max 115 mL). Median 24-hour uptake of I-123 prior to therapy was 68% (min 31%, max 96%). Median therapeutic dose of I-131 administered was 11.8 mCi (min 3.8, max 29.5 mCi), equating to a median of 0.31 mCi/mL (min 0.09, max 0.82 mCi/mL) based on thyroid volume and 24-hour uptake. For the subpopulation of patients with persistent hyperthyroidism after radioiodine therapy (vs. patients euthyroid or hypothyroid), median thyroid volume by ultrasound prior to therapy was 41.3 mL (vs. 21.2 mL, p=0.24). Median 24-hour uptake of I-123 prior to therapy was 69% (vs. 68%, p=0.63). Median therapeutic dose of I-131 administered was 13.9 mCi (vs. 11.3 mCi, p=0.39) equating to a median of 0.23 mCi/mL (vs. 0.31 mCi/mL, p=0.28).

Conclusions: In a multicenter series with non-standardized dosing of I-131 for treatment of pediatric Graves’ disease, the frequency of successful thyroid ablation was approximately 91% with a single therapy. Median administered dose was 11.8 mCi (~0.3 mCi/mL of thyroid). No significant predictors of failed ablation were identified in this study.