Malignancy risk associated with radioactive iodine therapy for Graves' disease.

Background: Radioactive iodine therapy (RAI) is a frequently chosen therapy for Graves' disease. The aim of this study was to determine whether RAI for Graves' disease increases the risk of thyroid malignancy.

Methods: A retrospective analysis was performed of all Graves' disease patients who underwent thyroidectomy at a single institution between 2013 and 2022. Comparative analyses were performed with cohorts based on RAI therapy as the primary grouping variable.

Results: 413 patients were identified, of which 38 received RAI prior to surgery. RAI treated patients were more likely to undergo surgery for known malignancy or indeterminate nodules. RAI patients were also more likely to have malignancies larger than 1 ​cm. Among RAI treated patients, those who developed malignancy were older at the time of Graves' diagnosis and received early RAI therapy.

Conclusions: Use of RAI for treatment of Graves' disease increases the progression of thyroid carcinoma, but not the prevalence. Older age and early RAI therapy may be risk factors for malignancy in RAI treated patients.