December 8, 2016

Study links lifestyle factors to formation of high-risk polyps

Lifestyle factors like cigarette smoking and red meat consumption are known to be associated with an increased risk of colon polyps that can lead to colorectal cancer.

Lifestyle factors like cigarette smoking and red meat consumption are known to be associated with an increased risk of colon polyps that can lead to colorectal cancer. Polyps are small growths on the lining of the colon, and while some polyps are harmless others can progress to cancer.

A new study led by Vanderbilt University Medical Center (VUMC) investigators found that eating red meat is strongly associated with development of a specific type of high-risk polyp, while regular use of non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin, ibuprofen or naproxen is associated with a reduction in risk of developing those same polyps. The study was published in a recent issue of the journal Gut.

“Cigarette smoking, red meat consumption and the use of NSAIDs are modifiable lifestyle factors, and focusing on primary prevention of these polyps through lifestyle changes may be an important health strategy,” said Martha Shrubsole, Ph.D., research associate professor of Medicine and lead author of the study.

Martha Shrubsole, Ph.D.
Martha Shrubsole, Ph.D.

Two distinct pathways to colorectal cancer have been identified, including the adenoma carcinoma pathway in which polyps can progress to larger lesions with the potential to become an invasive cancer. The more recently recognized serrated pathway is thought to start with hyperplastic polyps that transition to sessile serrated polyps (SSPs).

While less than 10 percent of polyps are SSPs, they are linked to 20 to 35 percent of all colorectal cancers. These SSP polyps also are more likely to be missed during screening colonoscopies because they are more commonly found in the right (proximal) side of the colon and tend to be flatter than some other types of polyps. So prevention of polyps, particularly SSPs, through lifestyle modification is an important health goal.

For this study, investigators used data from the Tennessee Colorectal Polyp Study, a colonoscopy-based, case-control study by Vanderbilt’s GI SPORE program whose participants were recruited between 2002 and 2010 at a time when SSPs were not uniformly recognized or diagnosed. The researchers newly reviewed all polyps, regardless of the initial diagnosis, to standardize the diagnoses. After review, the study included 214 SSP cases, 1,779 adenoma cases, 560 hyperplastic polyp cases and 3,851 polyp-free controls.

Telephone interviews were conducted during the original study to determine the participants’ medication use, family history and lifestyle factors.

Using the adjusted data, the investigators found that cigarette smoking status, duration and intensity were associated with increased risk for developing all types of polyps, but were more strongly associated with SSPs.

In comparison with those who never regularly used NSAID medications, current regular use of NSAIDs was associated with a 40 percent reduction in the risk of developing SSP polyps. Using NSAIDs for more than 10 years was more strongly associated with a reduced risk of SSPs than ADs.

While dietary patterns produced mixed results, the findings on red meat were most striking. Eating more red meat increased the risk of developing all types of polyps but the likelihood of developing SSPs was two times greater than the risk of developing the other types of polyps.

After adjustment for other factors, the risk of developing SSPs was not statistically significant for obesity, fiber, folate or fat intake, although there was a borderline statistical significance between fiber intake and a reduced risk of SSPs.

“This was the first study to extensively evaluate dietary risk factors for SSPs and we found for the first time that red meat was strongly associated with the likelihood of developing SSPs,” Shrubsole said.

The authors note that larger studies will be needed to confirm these findings.

Other authors include James Davenport, M.D., Ph.D., Timothy Su, M.D., Ph.D., Zhiguo Zhao, M.S., VUMC; Walter Smalley, M.D., MPH, Reid Ness, M.D., MPH, and Wei Zheng, M.D., Ph.D., MPH, VUMC and the Department of Veterans Affairs Tennessee Valley Healthcare System; and Helen Coleman, Ph.D., Queen’s University, Belfast, UK.

The study was supported by funding from the National Cancer Institute, a division of the National Institutes of Health (P50CA950103, R01CA97386, K07CA122451, R25CA160056, P30CA68485).