No Association between Cytochrome P450 and Glutathione S-Transferase Gene Polymorphisms and Risk of Colorectal Adenoma: Results from the UK Flexible Sigmoidoscopy Screening Trial

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Abstract
The study included 1,899 Caucasian individuals (1,267 males and 632 females), ages 55 to 64 years, who had undergone screening for polyps in the distal colorectum as part of the UK Flexible Sigmoidoscopy Screening Trial (2). The UK Flexible Sigmoidoscopy Screening Trial is a randomized controlled trial of 368,583 participants from 14 geographic regions, designed to test the efficacy of a once-only flexible sigmoidoscopy in the prevention of colorectal cancer. Individuals were invited to participate via their general practitioner. Of the 40,674 screened, 131 colorectal cancers were detected and excluded from the analysis. Other exclusion criteria included a history of colorectal cancer, adenoma, or inflammatory bowel disease; a severe or terminal disease with life expectancy of <5 years; and a sigmoidoscopy or colonoscopy within the past 2 years or incapability of providing informed consent. In the study presented here, cases were individuals with histologically confirmed adenoma of the distal bowel from three of the study centers (Leeds, Norwich, and Portsmouth). All adenoma cases were asked to provide a blood specimen, of which 94% agreed. Controls were age- and sex-matched individuals with a negative flexible sigmoidoscopy result (no adenomatous or hyperplastic polyps). Overall, blood samples were available for 918 cases and 981 controls.