Lifestyle factors such as cigarette smoking and red meat consumption are known to be associated with an increased risk of colon polyps that can lead to colorectal cancer. A new study led by Vanderbilt University Medical Center (VUMC) investigators expanded on that knowledge by discovering that eating red meat is strongly associated with development of a specific type of high-risk polyp.
[Photo: Dr. Martha Shrubsole]
Two distinct pathways to colorectal cancer have been identified, including the adenoma-carcinoma pathway in which adenomas 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 are also more likely to be missed during screening colonoscopies because they are more commonly found in the right side of the colon and tend to be flatter than some other types of polyps. Prevention of polyps, particularly SSPs, is an important health goal.
The researchers’ findings on the association of red meat consumption with the development of SSPs were striking. Eating more red meat increased the risk of developing all types of polyps, but the likelihood of developing SSPs was twice as high as the risk of developing other types of polyps.
The investigators also discovered 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. At the same time, however, regular use of non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen or naproxen, was associated with a reduced risk of developing those same polyps. Specifically, in comparison with those who never regularly used NSAIDs, current regular use of NSAIDs was associated with a 40 percent reduction in the risk of developing SSP polyps.
“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,” said Dr. Martha Shrubsole, Research Associate Professor of Medicine and lead author of the study. “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.”
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.
The study was published in the November issue of the journal Gut. To view a copy of the article, please go to https://www.ncbi.nlm.nih.gov/pubmed/27852795.