We have therefore tested the XRCC1 codon 399 and OGG1 codon 326 variant alleles in combination, but it showed no significant association with colorectal adenoma or cancer risk (OR 1.18, 95% CI 0.38–3.68; OR 0.91, 95% CI 0.54–1.52) (further data not shown). This evidence concerns the gene XRCC1 and colorectal adenoma.