Health Blog

Colon Cancer Screening

Colon (large bowel/large intestine) cancer is the third commonest non-skin cancer in both men and in women, and is our nation’s second leading cause of cancer death.

Colon Cancer Screening

By Ronald Musto, MD, MPH

Benjamin Franklin said, “An ounce of prevention is worth a pound of cure”. He was not talking about screening for colon cancer – but he could have been! Colon (large bowel/large intestine) cancer is the third commonest non-skin cancer in both men and in women, and is our nation’s second leading cause of cancer death. This is more than unfortunate because, in large measure, colon cancer is preventable.

Colon cancer begins as a colon “polyp” – a small growth inside the large bowel. There are several kinds of colon polyps. Not all polyps develop into bowel cancers, but all bowel cancer starts as a colon polyp. Finding and removing polyps before they “transform” into cancer, is the goal of colon cancer screening. Even if colon cancer is already present, the earlier it is detected, the greater the chance for cure. The earliest stage of colon cancer can be cured more than 95% of the time.

Several tests may be performed to detect colon polyps or colon cancer.

The test most likely, when performed by a skilled operator, to detect both colon polyps and colon cancer is colonoscopy. Colonoscopy is performed by a physician with a scope that is inserted into the rectum. The physician can see the entire colon directly. If the physician sees polyps, they are removed through the scope. Bowel cleansing and light sedation are used. Bowel perforation is a rare complication. Sigmoidoscopy is like colonoscopy except that only the lower 1/3 of the colon is seen and sedation is not used.

Air contrast barium enema is an X-ray examination of the colon after the instillation of air and enema fluid. Bowel cleansing is required. CT Colography is like a barium enema except that a CAT scanner is used to produce computer generated pictures of the colon. The risk of bowel perforation is extremely small.

High sensitivity occult blood testing requires that a sample of three or more bowel movements be smeared on a card and sent to a laboratory where chemicals are applied that detect the presence of unseen blood. Stool DNA testing requires that a sample of bowel movement be collected in a container and sent to a laboratory where it will be tested for the presence of abnormal genetic material that may indicate cancer. Stool tests entail no risk.

Colonoscopy is the best test for detecting both colon cancer and colon polyps, followed by CT colography, then air contrast barium enema, and sigmoidoscopy. Stool tests for blood or DNA are fair at detecting colon cancer, and are poor for detecting colon polyps.

The American Cancer Society currently recommends that people age 50 and older with an average risk for colon cancer select from among the following screening strategies.


every ten years

CT Colography

every five years

Air Contrast Barium Enema

every five years


every five years

Stool Occult Blood

every year

Stool DNA Test

once every 3 years

Colonoscopy must be performed after any other test that gives a positive result.

Earlier and/or more frequent screening is recommended for people who are at increased risk of colon cancer. Risks include personal risks (inflammatory bowel disease, hereditary poly syndromes, prior history of colon cancer or high risk polyps) and family history (colon cancer or high risk polyps, especially before age 50).

Speak, then, to your doctor about colon cancer screening. Choose a screening strategy with which both you and your physician are comfortable. Encourage your loved ones to do the same. Ben Franklin would be proud!

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