Gastroenterology

Screening for colorectal cancer

Learn the pros and cons of different tests

Colorectal cancer is a leading cause of cancer death. But when it's found at an early stage before it has had the chance to spread, the five-year survival rate is about 90%, according to the American Cancer Society (ACS).

The best way to find colorectal cancer early is through screening tests. The ACS says people of average risk should have their first test at age 45. How often you should be screened can depend on which test you choose.

Here are five testing options.

Colonoscopy

Colonoscopy is the only test that can both find and prevent cancer.

During the test, a narrow, flexible tube with a light and camera is inserted into your rectum and guided through your colon (don't worry, you'll be sedated). Small instruments can be passed through the scope to biopsy or remove any suspicious polyps.

Advantages of a colonoscopy include:

• It can biopsy and remove growths.
• It only has to be done every 10 years.
• It can help find some other diseases too.

Disadvantages include:

• A total bowel prep is needed.
• Sedation is needed.
• You'll likely miss a day of work.
• It costs more than other tests.
• There's a small risk of bleeding, bowel tears or infection.

CT colonography (virtual colonoscopy)

This test involves a CT scan of your colon and rectum. Special computer programs create a detailed view of the inside of the colon and rectum that can reveal polyps or cancer.

A colonography is not as invasive as a colonoscopy, but the same type of bowel prep is needed before the test.

Advantages of colonography include:

• It's fairly quick and safe.
• It only has to be done every five years.
• No sedation is needed.

Disadvantages include:

• A total bowel prep is needed.
• It can have false-positive results.
• You're exposed to a small amount of radiation.
• Polyps can't be removed during the test.
• If abnormalities are found, you'll need to have a colonoscopy.

Fecal immunochemical test (FIT)

The FIT checks for signs of cancer by looking for occult (hidden) blood in the stool.

Advantages of the FIT include:

• You don't have to clean out your bowel beforehand (bowel prep).
• You don't have to change your diet or medications before the test.
• You can do the test in the privacy of your home.
• There's no direct risk to your colon.
• It's fairly inexpensive.

Disadvantages include:

• The test can miss growths (polyps) in your colon that could be signs of cancer.
• It can have false-positive results.
• It needs to be done every year.
• If abnormalities are found, you'll need to have a colonoscopy.

Guaiac-based fecal occult blood test (gFOBT)

Another stool-based test, the gFOBT looks for signs of blood in the stool through a chemical reaction.

Advantages of the gFOBT include:

• No bowel prep is necessary.
• You can do the test at home.
• There's no direct risk to your colon.
• It's fairly inexpensive.

Disadvantages include:

• The test can miss growths in your colon that could be signs of cancer.
• It can have false-positive results.
• You need to make some changes in your diet and possibly medications too. For example, you'll need to avoid red meat for three days before testing.
• It needs to be done every year.
• If abnormalities are found, you'll need to have a colonoscopy.

Stool DNA test

Also a stool-based test, this looks for certain abnormal sections of DNA from cancer or polyp cells.

The stool DNA test needs to be done every three years.

Advantages of the stool DNA test include:

• There's no bowel prep.
• You can do the test at home.
• There's no direct risk to your colon.
• No diet or medication changes are needed.

Disadvantages include:

• The test can miss growths in your colon that could be signs of cancer.
• It can have false-positive results.
• If abnormalities are found, you'll need to have a colonoscopy.

Talk to your doctor about which test might be most appropriate for you. You also should check with your insurance plan to find out which tests are covered and at what age.

What risk factors do you have for colorectal cancer? Find out by taking this assessment.

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Sources: American Cancer Society; American Society for Gastrointestinal Endoscopy