A prospective study of cytochrome P450 1A1 polymorphisms and colorectal cancer risk in men.

Introduction Positive associations with increased red meat intake and colorectal cancer have been reported consistently (1), particularly with the consumption of broiled and grilled meats (2). This may be attributable to PAH formation. Cigarette smoking is another source of PAH exposure, and an association of early onset of smoking with adenomatous polyps (3), and less consistently, with colon cancer has been reported (3, 4). CYP1A1 codes for a protein (5) that converts PAHs to their ultimate DNA-binding forms. The only published study on the association between CYP1A1 and colorectal cancer risk reported a 7-fold increase in in situ colorectal cancer risk for the MspI variant genotype among Asians but not in Caucasians (6). In this prospective study, we tested whether Caucasian men with the variant CYP1A1 genotypes are at increased risk of developing colorectal cancer and whether the associations of red meat intake and smoking with colorectal cancer were modified by CYP1A1.