DNA double-strand break analysis by γ-H2AX foci: A useful method for determining the overreactors to radiation-induced acute reactions among head-and-neck cancer patients

Purpose: Interindividual variability in normal tissue toxicity during radiation therapy is a limiting factor for successful treatment. Predicting the risk of developing acute reactions before initiation of radiation therapy may have the benefit of opting for altered radiation therapy regimens to achieve minimal adverse effects with improved tumor cure. Methods and Materials: DNA double-strand break (DSB) induction and its repair kinetics in lymphocytes of head-and-neck cancer patients undergoing chemoradiation therapy was analyzed by counting γ-H2AX foci, neutral comet assay, and a modified version of neutral filter elution assay. Acute normal tissue reactions were assessed by Radiation Therapy Oncology Group criteria. Results: The correlation between residual DSBs and the severity of acute reactions demonstrated that residual γ-H2AX foci in head-and-neck cancer patients increased with the severity of oral mucositis and skin reaction. Conclusions: Our results suggest that γ-H2AX analysis may have predictive implications for identifying the overreactors to mucositis and skin reactions among head-and-neck cancer patients prior to initiation of radiation therapy.