Heterocyclic amines (HCAs), such as MeIQx, and PhIP, are produced in meats cooked at high temperatures. Case-control studies have found that the intake of meats and HCAs are associated with cancer of various sites, such as colorectal, stomach, lung, and breast. We investigated the relation of meat and meat-related carcinogens with risk of prevalent colorectal adenoma, a precursor of cancer, in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Dietary intake was assessed using a 137-item food frequency questionnaire with 10 additional questions on meat cooking methods. We estimated intake of different sub-groups of meat, MeIQx, and PhIP by linking the responses from the meat-cooking questionnaire module to a specifically developed database to determine exposure to these compounds. Based on the results of the initial sigmoidoscopy screening, 3,696 histologically verified adenoma cases of the left-sided large bowel and 34,817 controls with a negative screening result were included in the analyses. Red meat intake was not associated with increased risk of colorectal adenomas in all cases. However, there was an increased risk associated with red meat intake for advanced adenomas resulting in an odds ratio (ORs) of 1.30 (5th vs 1st quintiles; 95% confidence interval (CI) 1.03-1.65). Increase in risk with higher intake of well done red meat (5th vs 1st, 95% CI) was observed for all adenomas (OR 1.22, CI 0.99-1.27), non-advanced adenomas (OR 1.17, CI 1.00-1.36; n= 2271), single adenomas (OR 1.18, CI 1.02-1.35; n=2796), and adenomas of the colon (OR 1.16, CI 1.03-1.47; n=2474). Similar risk patterns were observed with respect to MeIQx and PhIP intake. For example, increased risk ranging from 12% to 20% was observed for all adenomas, and adenomas of the various sub-groups for PhIP intake when we compared the 5th to 1st quintile. We also observed an association between higher intake of bacon and sausage and increased adenoma risk. Our study of more than 3,500 screening-detected colorectal adenomas shows that red meat, meat cooked at high temperatures to produce HCAs, and possibly preserved meats are all associated with a moderate (12-30%) increased risk of colorectal adenomas.
[Proc Amer Assoc Cancer Res, Volume 45, 2004]