Evaluating the Malignancy Risk Associated with Radioactive Iodine Therapy: Balancing Clinical Benefit and Long-Term Safety

Radioactive iodine (RAI) treatment for thyroid disease may be a treatment option for patients with high-risk differentiated thyroid cancer (DTC) or hyperthyroidism caused by Graves’ disease, toxic multinodular goiter, and toxic adenoma. Despite being a common treatment modality for thyroid disease, the long-term risk of developing cancer after RAI treatment remains unclear. This narrative review aims to discuss current guidelines for the use of RAI in thyroid disease and evaluate current literature regarding the incidence of malignancy after RAI treatment. In those with hyperthyroidism, the evidence for increased risk of cancer after RAI remains mixed, with studies suggesting little to no increased overall cancer risk. However, some studies do demonstrate an increase in organ-specific cancers, including thyroid, breast, kidney, and gastric cancers. In those with DTC, systematic reviews and large meta-analyses demonstrate a small increase in relative risk of hematologic malignancy, corresponding to only a modest increase in absolute incidence. More recent evidence suggests that the risk of malignancy after RAI treatment may have a dose-dependent correlation. Current guidelines for the use of RAI should consider the risk of malignancy associated with this treatment modality.