Mei X, Yao X, Feng F, et al. - Using SEER registries, researchers sought to compute the relative risks (RRs) of subsequent malignancies (SMs) by different sites linked with radioactive iodine (RAI) treatment among differentiated thyroid cancer (DTC) survivors, by applying Poisson regression. They also assessed the attributable risk proportion of RAI for occurrence of different SMs. Total 4,628 of 104,026 DTC patients encountering a SM following two years of their DTC diagnosis, and observed for a medium follow-up time of 113 months, were identified. Large population based analyses were conducted and based on findings, it was inferred that SMs during follow-up would occur in a low percentage of DTC survivors. Albeit a slight increase in the adjusted RR of SMs development in patients undergoing RAI, a low attributable risk proportion linked with RAI was found, indicating that RAI-induced absolute number of SMs in DTC survivors would be low. The highest attributable risk proportion of RAI treatment was evident in hematological SMs, but when its low incidence among all DTC survivors was considered, the absolute number of hematological SMs was identified to be low.