XRCC1 and central nervous system cancer: It is reported that there were more than 300 SNPs in XRCC1 gene, and XRCC1 Arg194Trp and XRCC1 Arg399Gln polymorphisms are the most common studies SNPs.8,14 Many studies have indicated that the XRCC1 Arg194Trp polymorphism may influence the development of several kinds of cancer, including glioma and thyroid cancer,15,16 but several meta-analysis showed that no association between XRCC1 Arg194Trp polymorphism and risk of head and neck cancer, hepatocellular carcinoma, lung cancer and head and neck cancer.16-18