Colon cancer screening can detect polyps and early cancers. Such screening can find abnormalities that can be treated before cancer develops or spreads. Regular screenings may decrease deaths and prevent pain caused by colorectal cancer.

TOOLS OR TESTS

Several tools may be used, either alone or together, to screen for colon cancer:

The first method is a stool test that checks your bowel movements for blood.

• Polyps in the colon and smaller cancers often cause small amounts of bleeding that cannot be seen with the naked eye.
• The most common method used is the fecal occult blood test (FOBT). Newer stool tests are called the fecal immunochemical test (FIT) and stool DNA test (sDNA).

The second method is a sigmoidoscopy exam.

• This test uses a flexible small scope to look at the lower part of your colon. Because it only looks at the last one-third of the large intestine (colon), it may miss some cancers.
• A stool test and sigmoidoscopy should be used together.

The third method is a colonoscopy. A colonoscopy is similar to a sigmoidoscopy, but the entire colon can be viewed. You will usually be mildly sedated during a colonoscopy.

Two other methods may be used:

• Double-contrast barium enemy, a special x-ray of the large intestine, which includes the colon and rectum
• Virtual colonoscopy -- a type of x-ray that uses computer software to create an image

A test called capsule endoscopy (swallowing a small, pill-sized camera) is also being studied, but it is not recommended for standard screening at this time.

SCREENING FOR AVERAGE-RISK PEOPLE

There is not enough evidence to state which screening method is best. Discuss with your doctor which test is most appropriate for you.

Beginning at age 50, both men and women should have a screening test. Some health care providers recommend that African Americans begin screening at age 45.

Screening options for patients with an average risk for colon cancer:

• Colonoscopy every 10 years
• Double-contrast barium enema every 5 years
• Fecal occult blood test (FOBT) every year - if results are positive, a colonoscopy is needed
• Flexible sigmoidoscopy every 5 - 10 years, usually with stool testing FOBT done every 1 - 3 years
• Virtual colonoscopy every 5 years

SCREENING FOR HIGHER-RISK PEOPLE

People with certain risk factors for colon cancer may need earlier (before age 50) or more frequent testing.

More common risk factors are:

• A family history of inherited colorectal cancer syndromes, such as familial adenomatous polyposis (FAP) or hereditary nonpolyposis colorectal cancer (HNPCC)
• A strong family history of colorectal cancer or polyps. This usually means first-degree relatives (parent, sibling, or child) who developed these conditions younger than age 60.
• A personal history of colorectal cancer or polyps
• A personal history of chronic inflammatory bowel disease (for example, ulcerative colitis or Crohn's disease)

Screening for these groups of people is more likely to be done using colonoscopy.

See also: Colon cancer