Interindividual differences in radiation-induced apoptosis of peripheral blood leukocytes in normal individuals and breast cancer patients

Background: Quantification of radiation-induced apoptosis in peripheral blood lymphocytes (PBLs) has been proposed as a possible screening test for cancer-prone individuals and also for the prediction of normal tissue responses after radiotherapy. Materials and Methods: The neutral version of the comet assay (single-cell gel electrophoresis) was used 24, 48, 72 hours after irradiation with 8 Gy gamma rays to assess interindividual differences in gamma rays-induced apoptosis in peripheral blood leucocytes between a panel of 30 normal individuals, and 30 breast cancer patients who hadn’t received radiotherapy or chemotherapy previously. Slides were stained with ethidium bromide and comets were assessed using visual and computer analysis. Results: In all incubation times, the baseline and radiation induced apoptosis values were higher in breast cancer patients compared to normal individuals which were significantly different (p<0.01). Although, both baseline and radiation induced values were higher in young breast cancer patients, the age did not seem to have a significant effect on apoptosis values both in cancer cases and controls. Conclusion: The increased rate of apoptosis observed in the leukocytes of breast cancer cases might be associated with their deficient DNA repair mechanisms. This finding might indicate that the radiation induced apoptosis could have some predictive potential. However, large interindividual variation has been a drawback. More studies are required to investigate the causes of interindividual variation and how it might be minimized. Iran. J. Radiat. Res., 2012; 9(4): 237­244