Validation of sensitive assays for prediction of radiosensitivity in breast cancer therapy

Despite relatively low amount of patients analyzed so far (ten persons), the data have shown statistically significant increase in the background level of 53BP1 foci in breast cancer patients as compared to healthy persons (twenty persons). Our preliminary data are in line with the recent report and encourage studies of the DNA repair foci assay with the goal to select individuals for whom a detailed examination is necessary because of their increased susceptibility to breast cancer (Someya et al., 2006). Another interesting result was that the increased level of DSB repair foci was observed in the lymphocytes of breast cancer patients already at 24 h following first local fraction. This data provide evidence that the chosen technique is very sensitive to local irradiation though the samples for analysis were taken from the integral blood. Finally, similar increase in DSB repair foci was observed during the radiotherapy and even 1-3 month after radiotherapy. Based on these results the amount of samples may be limited by taking the blood only 24 h following first local fraction of radiotherapy. In this way, the procedure of the individual radiosensitivity evaluation may be significantly simplified.