XRCC1 and metastatic colorectal cancer: A 5-fold greater incidence of failure by 5-FU/oxaliplatin therapy had been reported for metastatic colorectal cancer patients with XRCC1 R399Q (QQ or QR) substitution compared with that of the RR genotype, suggesting that the polymorphism was associated with resistance to oxaliplatin/5-FU therapy [92].