Ask an expert: What you should know about polyps

Todd Crocenzi, M.D., answers frequently asked questions about polyps. Dr. Crocenzi is a medical oncologist and director of the Providence Gastrointestinal Cancer Research Program at Providence Cancer Center.

What is a polyp?
A polyp is a lump that forms in the inner lining of the colon. The lining of a healthy colon is continually updating itself, replacing older cells, as they break down, with new ones. The old cells are then sloughed off into the stool. If something disturbs the normal sloughing process, an abnormal group of these older cells can collect and form a polyp.

Are there different kinds of polyps?
Yes. Most polyps remain small and harmless – we call these hyperplastic polyps. But some develop other abnormalities and begin to grow unchecked – these are called adenomatous polyps. We refer to adenomatous polyps as pre-cancerous polyps because they are not cancerous yet, but they have the potential to become cancerous. Given enough time to grow and develop, some adenomatous polyps can spread into surrounding tissues and infiltrate the two highway systems of the body: the bloodstream and the lymph nodes. This ability to invade and spread, or metastasize, is how we define a cancer.

Does having a polyp mean that I will get cancer?
No, but it does increase your risk. Most polyps – even the adenomatous type – do not turn into cancer. However, nearly all colorectal cancers that do develop start out as polyps. That’s why we remove all polyps when we find them during screenings. Removing a polyp early makes sure that it will never have the chance to turn into cancer. People who have had polyps in the past are more likely to form additional polyps – that increases the risk of a future cancer and makes regular screenings even more important.

Can you tell after you remove a polyp whether or not it’s the kind that would have turned into cancer?
Yes – all polyps are tested after they are removed, and the tests determine what types of polyps they are.

Why do some people get polyps while others don’t?
That’s currently unknown, which is why regular screening is important for everybody.

How long does it take a polyp to turn into a cancer?
Generally, it’s about a 10- to 15-year process, which explains why getting a colonoscopy screening once every 10 years is sufficient for most people. However, this chain of events may occur faster in people with hereditary colorectal cancer syndromes. For these people and others at high risk for colorectal cancer, more frequent screening is usually advised.

Can a high-fiber diet prevent polyps?
While a diet high in fiber is beneficial on multiple levels and highly encouraged, the research to date has not been able to prove an association with reduced risk of polyps or colorectal cancer.

Is there any way to prevent polyps from forming?
For people who have had colorectal cancer, a low-dose “baby” aspirin (81mg) once a day may reduce the risk of developing new adenomatous polyps and cancers. Another anti-inflammatory called celecoxib (Celebrex) also is used to reduce the risk of polyps and cancer in people with an inherited condition called familial adenomatous polyposis, or FAP. Studies are currently underway to determine whether or not people at average risk of colon cancer would benefit from these or other preventive medicines.

Until we learn more, there may not be much you can do to prevent the formation of polyps, but there is plenty you can do to prevent them from becoming cancerous. I may sound like a broken record, but it bears repeating: Regular colorectal cancer screenings give you the best possible chance of finding polyps and removing them before they ever have the chance to turn into cancer. This important step, plus three others – getting regular exercise, maintaining a healthy weight and avoiding tobacco – could prevent as much as 90 percent of all colorectal cancer. That’s music to my ears.


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