Screening Tests for those at Average Risk

Most experts agree that colorectal cancer is an illness uniquely suited to the use of screening tests. There are several reasons:

• The illness is common.

• It is lethal if left untreated.

• Early detection dramatically improves survival.

• Abnormal growths (polyps) may be present in the colon and rectum for many years without spreading, providing a lengthy opportunity for early detection.

• Polyps and early colorectal cancer, which have not spread beyond the lining of the bowel wall, are very treatable, with a cure rate close to 100 percent.

• Simple screening tests are available.

There is a still debate, however, about the most efficient means of screening the large group of people who are at average risk for colorectal cancer. Screening tests include:

Fecal Occult Blood Test
A fecal occult blood (FOB) test detects blood in the stool even if the amounts are too small to be visible to the naked eye. The drawbacks of FOB tests are that they do not always detect colorectal cancers and most people who have positive FOB tests do not have colorectal cancer, as there are many causes of gastrointestinal bleeding. For example, polyps, ulcers and hemorrhoids may also cause positive FOB tests, as will blood in the meat that a person has eaten. An FOB test can be useful, however, because it can provide an early warning of colorectal cancer.

If you are having an FOB test, you must avoid eating meat for several days before the test. You should also avoid medications like Aspirin, which can cause a small amount of blood loss in the stool. For this test, you will be asked to collect three stool samples at home, and take them to the laboratory for testing.

Flexible Sigmoidoscopy
This procedure examines the rectum and the lower part of the colon, with a flexible tube carrying a tiny video camera. A biopsy can be performed, if needed. The tube does not extend the entire length of the colon and will, therefore, not detect polyps or cancer farther up the colon. If a polyp is found, a colonoscopy should be done to examine the rest of the colon.

Your doctor will tell you how to prepare for a sigmoidoscopy. Preparation usually takes the form of a liquid diet for 12-24 hours before the procedure, a laxative and an enema. This will clean out your lower colon so your doctor can see it clearly during the sigmoidoscopy. The test can be done in a clinic or in a doctor's office, and will take about 15 minutes. You may experience some cramping during the exam, but will be able to return to your regular activities later in the day.

Many provinces are either considering or have already established programs to screen for colorectal cancer.

The Canadian Cancer Society recommends that all men and women who are 50 years and older and at average risk for colorectal cancer have a fecal occult blood test every two years. If abnormalities are found, followup testing should include a colonoscopy, a double contrast barium enema or a sigmoidoscopy.

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