Use of Apoptotic Biomarkers to Predict Response to Radiotherapy in Breast Cancer Patients

Introduction: To enhance radiation therapy efficiency it is crucial to implement an individual-based treatment. The aim of present study was to identify the mechanism of intrinsic apoptosis pathway on radiosensitivity and normal tissue complications caused by the radiotherapy.   Materials and Methods: radiation-induced apoptosis in peripheral blood mononuclear cells derived from unselected breast cancer (BC) patients was examined using the relative quantitative RT-PCR. Expression levels of Bax, Bcl-2, and Bax/Bcl-2 ratio (as an in-vitro radiosensitivity index (RSI)) were examined in in-vitro irradiated (1 and 2 Gy) cells. All the patients received similar tangential irradiation of the whole breast and conventional fractionation and then, Clinical radiosensitivity (as a clinical radiosensitivity index) was determined using the acute reactions to radiotherapy of the skin according to RTOG score. All statistical analyses were performed using GraphPad Prism, version 7.01. Results: The notable result was a significant correlation between dose-response curve slope (in-vitro RSI) and acute skin toxicity score following irradiation (clinical RSI). Conclusion: These data suggest that Bax/Bcl-2 ratio determination before radiation therapy can be used as a potential biomarker to identify radiosensitive individuals. However, further studies are required to validate radiation-induced apoptotic biomarkers.