Blood cells in thyroid cancer patients: a possible influence of apoptosis

The side effects of radioactive iodine (131-I) treatment of differentiated thyroid cancer (DTC) patients include reduction of peripheral blood cell counts. The aim of this study was to analyze some potential changes in blood cell counts of DTC patients after 131-I therapy, especially CD3-positive, CD19-positive, and CD56-positive peripheral blood lymphocytes (PBL), as well as the possible role of apoptosis in selected lymphocyte populations. The study group included 24 thyroid cancer patients and 24 control subjects. Peripheral blood samples from patients and controls were analyzed using 5-color flow cytometry. Apoptotic cells were detected using an Annexin V-FITC/7-AAD kit. There was a statistically significant decrease of all blood cells after the 131-I therapy. The CD19+ B lymphocyte population was the most affected (5.82 ± 3.21% before therapy vs. 3.93 ± 2.60% after therapy, p = 0.008). This decrease was correlated with the degree of apoptosis of peripheral blood lymphocytes (Spearman's r = 0.563, p =0.013). We concluded that 131-I therapy of DTC patients led to a decrease of all peripheral blood cells, especially CD19+ B lymphocytes. This directly correlated with apoptosis of PBLs, indicating that radiation damage to B cells leads to subsequent elimination by apoptosis.