Colorectal Polyp Type and the Association with Smoking, Charred Meat Intake and mEH

New research on the relationship between diet, lifestyle, genetics and colorectal cancer reinforces broad screening for adenomas, precursor lesions for colorectal cancer was presented today at AACR 2009, Denver. It also provided rationale for further research evaluating the risk of colorectal cancer associated with certain hyperplastic polyps, common polyps traditionally thought to be clinically unimportant.

“Colorectal cancer is the second leading cause of cancer death among men and women, and you can make great strides towards eliminating it with proper screening,” said Andrea N. Burnett-Hartman, a doctoral student at Fred Hutchinson Cancer Research Center in Seattle. Researchers recruited 529 patients with adenoma, 691 patients with hyperplastic polyps, 227 patients with adenomas and hyperplastic polyps, and 772 healthy control patients. These patients were asked a variety of lifestyle questions using a questionnaire and analyses were performed. Burnett-Hartman and colleagues studied the risk of hyperplastic polyps and adenomas associated with cigarette smoking, charred red meat intake and variations in the mEH gene; a gene responsible for processing some of the carcinogens found in cigarette smoke and charred meat.

Although both adenomas and hyperplastic polyps had elevated risks associated with cigarette smoking, the association for hyperplastic polyps was stronger than for adenomas. If a patient had smoked at least 22 pack-years (one pack-year is equal to smoking one pack per day for one year), the risk of adenomas increased by 68 percent while the risk of hyperplastic polyps increased 2.38-fold.

For current smoking status, the risk increase was also 68 percent for adenomas; while the risk of hyperplastic polyps increased 3.02-fold. Frequency of charred red meat consumption was consistently associated with slightly elevated risks in all polyp groups, but this association was not significant. Also, there was no link between polyps of any type and variation in the mEH gene. “Colon cancer has a very strong environmental component, but based on the results of our study, these common gene variants do not significantly protect an individual from the carcinogenic effect of smoking,” said Burnett-Hartman.