Predictive factors of cytotoxic damage in radioactive iodine treatment of differentiated thyroid cancer patients

Radioactive iodine (I-131) therapy in patients suffering from differentiated thyroid cancer (DTC) is a targeted treatment commonly used for thyroid ablation and locoregional and distant metastatic spread management. Despite a significant proportion of the I-131 dose entering the circulation, there is currently no detailed information regarding its effect on the blood cell system. In order to assess the cytotoxic effects of I-131 therapy on the circulatory system, blood cell levels, thyroid-related hormones and CD45(+) cell cytotoxicity were estimated in blood collected from patients with DTC. The micronuclei (MN) frequency of the peripheral blood CD45(+) cell fraction was significantly increased after 30 days of I-131 therapy compared to that prior to treatment, although a strong individual variation was observed. A significantly negative correlation between MN frequency and the level of platelets and plateletcrit was observed; however, there was no such correlation with thyroid-related hormones. These results suggest that the correlation between MN frequency and the platelet system may serve as a biomarker of exposure and, possibly, of sensitivity in DTC patients undergoing I-131 therapy following thyroid and lymph node surgery.