Q. How can I be screened for colon cancer?

A. There are 4 basic ways to be screened for colon cancer, and which one is right for you depends on several factors.

Occult Blood: This test entails checking the stool for hidden blood by smearing some stool on a special paper. The doctor then puts liquid on the paper. If the paper turns blue, there is blood in the stool, and additional tests are needed. This test is fairly easy, but it misses a lot of cancers and pre-cancers. Overall, you can reduce your risk of dying from colon cancer by 30% if you have your stool checked this way every year.

Sigmoidoscopy: In this test a small, flexible tube is place inside the rectum. The doctor looks at the lining of the intestine to see if he can see a polyp (that may develop into a cancer) or an early cancer. If an abnormality is found, another test is needed to remove the polyp or cancer. The test is very well tolerated, but it misses about half the polyps and cancers because the tube is not long enough to see the entire colon. Overall, you can reduce your risk of dying from colon cancer by about 45% if you have a sigmoidoscopy every 3-5 years.

Barium enema: This test involves taking x-ray pictures of the intestine. It is an excellent test, able to find essentially all of the polyps and cancers. Many people do not like it, however, because they find the necessary bowel preparation and the taking of the pictures to be uncomfortable. Overall, you can reduce your risk of dying from colon cancer by about 90% if you have a barium enema done every 5-10 years.

Colonoscopy: While colonoscopy is probably the "best" test in terms of finding polyps and preventing colon cancer deaths, it is only a little better than the barium enema. The price you pay for this extra benefit is a more dangerous procedure. About 1 in every 500 patients with a colonoscopy ends up with a hole in her intestine. This is a high risk. (The same complication occurs about once every 40,000 barium enemas.)

Which method is right for you? In part it depends on your risk and your fear of colon cancer. In part it depends on your wish to avoid invasive tests. As you can see, with each test comes more success at preventing the disease, but you also have a more aggressive test.

You can learn more about colon cancer screening by occult blood and sigmoidoscopy at http://www.cancertest.com/screening.html and more about Medicare coverage of colon cancer screening at http://www.mgh.org/press/colon1.html.

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