XRCC1 and cancer: In the present study we used a case-control design to test the association between five amino acid substitution variants of DNA repair genes, XRCC1 (Arg194Trp), XRCC1 (Arg280His), XRCC1 (Arg399Gln), XRCC3 (Thr241Met) and XPD (Lys751Gln), and colorectal adenoma/cancer risk in a Norwegian cohort.