XRCC1 and alcohol dependence: Several studies have demonstrated that factors such as gender, smoking, alcohol use and H. pylori infection enhance the risk of stomach cancer for some XRCC1 genotypes, but not for others [24, 25].This is inconsistent with our study, although we found that smoking and alcohol consumption modify the effect of XRCC1 gene on the risk of stomach cancer in our sample, we could not demonstrate these effects to be statistically significant.