XRCC1 R399Q polymorphism and risk of normal tissue injury after radiotherapy in breast cancer patients
PURPOSE To evaluate the impact of functional polymorphisms in genes related to DNA repair mechanisms (XRCC1, TP53, MSH2, MSH3, XPD), oxidative stress response (GSTP1, GSTA1, eNOS, SOD2) and fibroblast proliferation (TGFβ1) on the risk of acute skin toxicity in breast cancer patients receiving radiotherapy. MATERIAL AND METHODS Skin toxicity was scored according to the Radiation Therapy Oncology Group criteria in 286 breast cancer patients who received radiotherapy after breast conserving surgery. Genotyping was conducted by PCR-RFLP analysis and real-time PCR allelic discrimination assay on genomic DNA extracted from peripheral blood. RESULTS In the multivariate analysis, nominally significant associations, before multiple testing corrections, were found between XRCC1 T-77C (T carriers vs. CC, OR: 2.240, 95% CI: 1.015-4.941, P=0.046), eNOS G894T polymorphisms (TT vs. G carriers, OR: 2.473, 95% CI: 1.220-5.012, P=0.012), breast diameter (OR: 1.138, 95% CI: 1.001-1.293, P=0.048), boost dose-fractionation (3 Gy vs. no boost, OR: 4.902, 95% CI: 1.458-16.483, P=0.010) and ≥ grade 2 acute radiation skin toxicity in breast cancer patients. CONCLUSIONS As our exploratory study suggests that XRCC1 T-77C and eNOS G874T may confer an increased risk of acute skin reactions to radiotherapy in breast cancer patients, further confirmatory studies are warranted to determine the clinical significance.