In response to the lack of consensus in the literature regarding the value of these enzymes’ expression in tumors as predictive biomarkers in NSCLC [24], the IFCT 0002 Phase 3 randomized trial, with its large patient sample (528 patients enrolled between 2001 and 2005) and the homogeneity of their treatments, constituted further opportunity to assess whether or not XRCC5, MSH2, BRCA1, and O6MGMT represent reliable biomarkers in Stage I and II NSCLC patients, treated with taxane- or anti-metabolite-based perioperative chemotherapy. This evidence concerns the gene XRCC5 and non-small cell lung carcinoma.