XRCC1 and breast cancer: When the joint effect of the XRCC1-280, XRCC1-399, and XPD-751 genotypes was studied, a statistically significant increase in the risk of breast cancer was seen for subjects carrying two at-risk genotypes of these genes (OR 1.54, 95% CI 1.00–2.37) compared to subjects with the wild-type genotypes for all three polymorphic sites (Table 5).