Hard-to-see polyp long thought benign may account for third of colorectal cancers, doctor warns

It has long been known that colon polyps are the start of colon cancers. It was thought that serrated polyps, however, do not become cancerous. Now Dr. James East, a gastroenterologist at Mayo Clinic Healthcare in London, says that line of thinking is outdated. Scientists believe these polyps do in fact play a significant role in cancer development.

“Our view of serrated polyps has come a long way in the last two decades, moving from seeing them as benign lesions that do not develop into cancer, to recognizing them as lesions that may account for up to one-third of all colorectal cancers,” East writes in a commentary in the journal Gut.

Serrated polyps are sawtooth-edged growths in the colon that are flat, nearly translucent, and can be difficult to visualize during colonoscopy. New research suggests that people with serrated polyps should be evaluated more frequently for transformation into cancerous lesions.

The colon, sometimes called the large bowel or large intestine, extends from the end of the small intestine in the right lower quadrant of the abdomen to the right upper quadrant, then to the left upper quadrant, then inferiorly to the anus. The regions of the colon as it reaches the anus are called the sigmoid colon and the rectum. 

Colon cancers, (or colorectal cancers, when they occur in the rectum) frequently start as small, benign polyps which are asymptomatic. Screening for colon cancer involves detecting and removing polyps before they transform into cancer. There are different kinds of polyps, and until the relatively recent past, physicians were unconcerned about serrated polyps.

Little research has been available to determine whether people with serrated polyps need more frequent screening for colorectal cancer.  Dr. Dan Li and colleagues at Kaiser Permanente, just published a newer, large study in Gut, which suggests that people with serrated polyps alone, or with another type of polyp called adenomas, may need more frequent colonoscopies, East says.

Adenomas are the most frequent type of polyp responsible for colon cancers. The Kaiser Permanente study shows that serrated polyps increase cancer risk by about the same degree of risk as adenomas. East says that the presence of both types of polyps in an individual raises even greater risk for colon cancer than either polyp type alone. Additional research is needed to assess cancer risk more accurately in people with serrated polyps, East says.

Rather than measuring risk for colon cancer according to the type of polyp present,  focusing on other markers for colon cancer may improve accuracy in assigning risk, states East. These markers include: the number of polyps, obesity, a high-fat diet, smoking, heavy alcohol use, and inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis, he adds.

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