Grillo Center: Colonoscopy, colon polyps and colon cancer risks

By Sue Smith

Q: I had a polyp removed at my last colonoscopy. Does this mean I will get colon cancer?

A: Colon polyps are abnormal growths that develop in the lining of the colon (large intestine). They are usually discovered during a colonoscopy because they typically do not cause any symptoms. Colon polyps are very common, occurring in 30 to 50% of adults. Older people are more likely to have colon polyps, which is why screening colonoscopy is recommended for those over 45. There are some hereditary disorders in which younger people are predisposed to colon polyps, and in these cases screening colonoscopy is started at an earlier age.

Removal of colon polyps (polypectomy) is routinely performed when they are identified at the time of colonoscopy. A flexible instrument is passed through the colonoscope, and the polyps are snipped off. This is a painless procedure with very few complications — namely occasional bleeding and rarely perforation of the colon wall (estimated to occur in about 1 out of 1,000 colonoscopies). The latter complication could require surgical repair. After removal, polyps are sent to a pathologist who determines their type based on a microscopic examination.

There are two main types of polyps: hyperplastic polyps, which are benign and adenomatous polyps (adenomas), which have the potential to become colon cancer. Only about 5% of adenomas will progress to cancer and even when this happens, it takes many years. Of course, once a polyp is removed, there is no chance for cancer to develop in that particular polyp. However, people who are found to have adenomas face a higher probability of developing more adenomas, and hence their risk of colon cancer is increased.

A person’s risk of developing colon cancer is based on the number, type, and size of the polyps that are removed during colonoscopy as well as the polyp’s microscopic appearance. These factors also determine when a follow-up colonoscopy is scheduled. In general, closer monitoring is recommended for adenomas, multiple polyps or large polyps because these are more likely to progress to cancer.

The following lifestyle factors may reduce the risk of developing colon polyps and colon cancer:

Eating a low-fat, high-fiber diet with lots of fruits and vegetables
Exercising regularly
Maintaining a normal body weight

Consumption of red meat, tobacco and excess alcohol have all been associated with an increased risk of developing colon cancer.

The bottom line is that removal of precancerous colon polyps dramatically lowers the risk of colon cancer because almost all colon cancer begins in polyps. Screening colonoscopy is the best tool for colon cancer prevention.

Sue Smith volunteers with the Grillo Center, which offers free, confidential research to assist in health understanding and decisions. To use this service, contact the grillocenter.org or 303-415-7293. No research or assistance should be interpreted as medical advice. We encourage informed consultation with a health practitioner.