FDA has cleared, or approved, several screening and diagnostic methods for colorectal cancer. When performed regularly, these tests allow the removal of polyps before they become cancerous, which can reduce the incidence of colon cancer by 40 percent. And, by preventing tumor formation, these tests can cut the death rate from colorectal cancer in half.

Screening for patients with no medical or family risk factors should begin at age 50 and be performed regularly. Available screenings include:

Fecal occult blood test. Both colon cancer and polyps can cause bleeding, which will be passed into the stool. In this test, a small stool sample transferred to a collection card with a narrow stick is screened for the presence of blood. The sample can be collected at home by patients, who send it to their doctors, or by the doctor during a physical examination. Because other conditions, such as stomach ulcers and hemorrhoids, can cause blood in the stool, this test has a high rate of false positives and may result in unnecessary follow-up screenings. It may also fail to detect some tumors.

Barium x-ray. In this test, a contrast material is infused through the rectum, This material expands the colon and allows a radiologist to see large polyps or cancers (greater than 10 millimeters) in the entire colon. The bowel must be cleansed by laxatives or enemas before the test is performed. This test involves some discomfort and often fails to detect small polyps.

The American Cancer Society recommends that patients over 50 have a fecal occult blood test yearly and a sigmoidoscopy every five years. Since Medicare and some, insurance companies pay for barium x-ray screening, many physicians also recommend that this test be used in conjunction with the flexible sigmoidoscopy. A colonoscopy should be performed if any abnormalities are seen, or if the patient is experiencing symptoms. Patients with known medical risk factors should be screened more extensively and more often.

Despite the availability of screenings and their relative effectiveness, the mortality rate for colorectal cancer remains high. Experts say there are several reasons for this, including the fact that some screenings may fail to detect tumors. Another reason, according to David Ahlquist, M.D., professor of medicine and director of the Colorectal Neoplasia Clinic at the Mayo Clinic in Rochester, Minn., is a reluctance of patients to have the tests performed due to the discomfort and embarrassment involved. "We could have a much larger impact on this disease if the screening tools we have were more widely used," Ahlquist says. "There's a challenge for science to come up with screenings that are more accurate and more comfortable so more people will have them performed."

Last updated Nov 26/06