Association of secondary hematologic malignancies with radioactive iodine therapy for differentiated thyroid cancer: A systematic review and meta-analysis of retrospective cohort studies.

e18076 Background: Radioactive iodine (RAI) ablation therapy is a minimally invasive yet effective intervention for treating differentiated thyroid cancer (DTC), however, its association with second primary malignant neoplasms continues to warrant concern. Moreover, current evidence for association with hematologic malignancies is limited. Aims and Objectives: This systematic review and meta-analysis aimed to evaluate the odds of secondary hematologic malignancies in DTC patients following RAI exposure. Methods: Following PRISMA guidelines, a systematic literature search was conducted on the following databases: PubMed and Web of Science to identify relevant studies that met the inclusion criteria from inception to January 2026. All statistical analyses were performed using R 4.5.2 using a random-effects model, and heterogeneity was assessed using the I 2 statistic. Results: Nineteen eligible studies comprising 642,218 DTC patients (RAI treatment group, n = 305,225; non-RAI treatment group, n = 336,993) were included in the final meta-analysis. The pooled odds ratio for secondary hematologic malignancies among patients treated with RAI was higher (OR = 1.25, 95%CI 1.12 to 1.39, P < 0.0001) compared to non-RAI group with high statistical significance and low heterogeneity ( I 2 = 8.4). Further subgroup analyses were performed based on different subtypes of haematologic malignancies. The odds ratio estimates for each subtype except for leukemia (OR = 1.48, 95%CI 1.11 to 1.98, P = 0.0082) were non-significant: Hodgkin’s lymphoma (OR = 1.27, 95%CI 0.68 to 2.38, P = 0.4557), myeloma (OR = 0.89, 95%CI 0.64 to 1.25, P = 0.4994), non-Hodgkin’s lymphoma (OR = 1.04, 95%CI 0.82 to 1.32, P = 0.7523). Conclusions: This meta-analysis suggests higher odds of secondary hematologic malignancies, especially leukemia, in DTC patients treated with RAI ablation therapy. However, further large-scale, multicenter prospective studies are needed to validate these findings.