XRCC4 and colorectal carcinoma: Given that all three polymorphisms, XPD G751A, hOGG1 C326G and XRCC4 G1394T, were not found in any individual, we examined the pairwise joint effect of variant alleles of XPD G751A, hOGG1 C326G and XRCC4 G1394T on CRC risk (Table 3).