Risk of primary breast cancer in patients with differentiated thyroid cancer undergoing radioactive iodine therapy: a systematic review and meta-analysis

Purpose: Although it has been proven that radioactive iodine (RAI) treatment is an effective and well-tolerated procedure in patients with differentiated thyroid cancer (DTC), there is still some concern regarding the risk of developing a second primary malignancy after RAI administration. We performed a systematic review and meta-analysis to investigate the risk of primary breast cancer in patients with DTC undergoing RAI therapy. Methods: A comprehensive literature search of the PubMed, Scopus, and Web of Science databases was conducted according to the PRISMA statement. Results: The final analysis included 14 studies accounting for a total of 200,247 patients with DTC (98,368 treated with RAI and 101,879 not treated with RAI). The relative risk of primary breast cancer in patients with DTC treated with RAI to those not treated with RAI among studies ranged from 0.45 to 2.55, the pooled relative risk was 0.83 (95% confidence interval, 0.70–0.99), and the heterogeneity was 71.5%. Conclusion: The present meta-analysis indicates that patients with DTC treated with RAI do not have a higher risk of primary breast cancer compared to those not treated with RAI. These findings suggest that RAI therapy does not increase the risk of breast cancer.