How to Prevent Colon Cancer
by Beth G. Hodges, MD

How does a person prevent colon cancer?

Early detection, especially if there is a family history of colon cancer or precancerous colon polyps is the key. In many cases, colon polyps can be found a removed before becoming cancerous.

How are colon polyps found?

The screening process for "normal risk" people (those without a family history like that listed above) can begin with digital rectal exam, where a physician palpates the opening of the rectum for masses and then takes a sample of stool to test for hidden evidence of blood. Additional stool cards can be sent home with the patient for repeated tests for hidden blood (usually three samples collected by the patient and returned to the provider's office for evaluation. This can be done yearly.

If occult blood is found in the stool, there is a 30-40% chance of a colon polyp being present and a 3-5% chance of a colon cancer. The presence of occult blood in the stool is an indication for further testing to rule out colon cancer.

Part or all of the colon can be evaluated by direct visualization with a colonoscope. A flexible sigmoidoscopy looks at the last half (ideally 60 centimeters) of the colon, while a colonoscopy evaluates the entire colon.

Obviously, because it evaluates the entire large bowel, a colonoscopy is a more complete test. Disadvantages to colonoscopy over flexible sigmoidoscopy are that colonoscopy is more expensive. It often takes place in a hospital outpatient setting, requires more preparation by the patient, and uses sedation (which means the patient loses an entire day of work.)

Flexible sigmoidoscopy has long been considered adequate for screening of a "normal risk" individual if done every 3-5 years and combined with annual fecal occult blood testing. A proximal colon polyp may be missed, but most patients with a tendency for colon polyps have them throughout the colon. If a polyp is found distally by flexible sigmoidoscopy, a full colonoscopy should always follow to evaluate the part of the colon not yet seen.

Virtual colonoscopy has limited use. It is essentially a very detailed CT scan of the colon to look for polyps. Most insurance plans are reluctant to cover this very expensive procedure and have so far mostly only done so when a patient could not have a traditional colonoscopy for some reason. One of the main disadvantages is that while the virtual colonoscopy may see the polyp, it cannot remove it or test for the polyp's cancer potential.

When should colon cancer screening start?

Average risk patients should begin at age 50. High risk individuals should begin at age 40 or 10 years before the earliest age of colon cancer diagnosis in the family or 5 years before the earliest age of discovered precancerous polyp. There are some rare types of hereditary colon cancer syndromes that warrant even earlier screening, best determined by a colon specialist (gastroenterologist.)

Other proven helpful ways to decrease the risk of or prevent colon cancer include a low fat diet, maintaining a healthy weight, and consuming a diet high in fiber. It is felt that a high fiber diet acts like a pipe cleaner through the colon, sweeping out toxins before they can build up.

Published - October, 2009