Background: Genetic polymorphisms in metabolizing enzymes may modify the association of environmental exposure on colorectal cancer (CRC) and adenoma risk.
Materials and methods: One hundred and ninety-eight CRC cases, 422 adenomas (206 low-risk and 216 high-risk adenomas) and 222 controls were genotyped for the CYP1A2 164 A-->C polymorphism and questionnaires were used to assess environmental exposure.
Results: The smoking parameter "current smoking" was significantly associated with CRC risk, and all the smoking parameters related to current smoking, having ever smoked or high numbers of cigarette years were significantly associated with risk of adenomas. No association was detected between red meat consumption or how well red meat was cooked and colorectal carcinogenesis. When stratifying the case groups based on CYP1A2 genotype, all the smoking parameters yielded stronger risk association in carriers of the C allele.
Conclusion: These findings may indicate that the association between cigarette smoking and colorectal carcinogenesis can be modified by the CYP1A2 genotype.