Colon Cancer and Rectal Cancer Screening: What Are the Options?

a woman and her mother go over colonoscopy results with a nurse

No one looks forward to a colonoscopy, or the bowel prep that goes with it. But colon cancer and rectal cancer screening – testing to look for cancer before symptoms start – helps saves lives.

Screening can find colon cancer or rectal cancer early when it’s small and easier to treat, or even prevent it altogether.

Colonoscopy, however, is just one of many tests that can be used to look for colon cancer and rectal cancer. And doctors and researchers continue to develop new ones.

Stool DNA test

A new type of non-invasive test to check for colon cancer and rectal cancer is available now, and may appeal to people who want to be screened, but don’t want to undergo the usual preparation required for a colonoscopy and some other screening tests. It’s called a stool DNA test because it looks for certain gene changes that are sometimes found in colon cancer and rectal cancer cells.

The FDA approved a stool DNA test called Cologuard in 2014. The patient uses a kit at home to collect a stool sample and mail it to a lab. The test checks for DNA changes that could be a sign of cancer or pre-cancerous growths called polyps. It also checks for blood in the stool, which can be a sign of cancer.

No special diet or bowel preparation (no laxatives or enemas) are required for a stool DNA test. However, if the Cologuard test does show a possible cancer or pre-cancer, the patient would then need a colonoscopy to confirm it, and possibly to remove any polyps.

Not everybody can have this type of screening test. It’s only for people with an average risk for colon or rectal cancer: no personal history of pre-cancerous polyps, colon or rectal cancer, or some other colon problems. Ask your doctor to be sure.

Tried-and-true screening tests

There are several more common tests that can be used to screen for colon and rectal cancer. Some are less able to find polyps and more likely to find cancer. Other tests not only can find cancer, but also are better at finding polyps; these tests may be more likely to prevent colon or rectal cancer.

Tests that can find polyps and cancer:

  • Colonoscopy uses a flexible lighted tube with a small camera on the end to look at the entire length of the colon and rectum. If polyps are found, they may be removed during the test. To prepare for the test, you may be asked to follow a special diet for a day or two before the test. You will also need to clean out your colon with strong laxatives (called a bowel prep) and sometimes with enemas, as well. Most people are sedated during the test. If nothing is found during the test, you won’t need another one for 10 years.
  • Flexible sigmoidoscopy is much like colonoscopy, but looks at only part of the colon and rectum. If polyps are found, they may be removed during the test, or you may need to have a colonoscopy later. Bowel prep may be required, but is not as extensive as the one used for colonoscopy. Most people do not need to be sedated during this test. If polyps or suspicious areas are seen, a colonoscopy will be needed to look at the rest of the colon. Flexible sigmoidoscopy must be done every 5 years.
  • Double-contrast barium enema is a type of x-ray test. It involves putting a liquid called barium into the rectum, which spreads through the colon. Air is then pumped in to spread the barium in a thin, smooth layer to show better detail. Then x-rays are taken. It requires bowel prep, but no sedation. If polyps or suspicious areas are seen on the test, a follow-up colonoscopy will be needed. Barium enemas also need to be repeated every 5 years.
  • CT colonography (also called virtual colonoscopy) is a scan of the colon and rectum that produces detailed cross-sectional images so the doctor can look for polyps or cancer. It requires bowel prep, but no sedation. Air is pumped into the rectum and colon, and then a CT scanner is used to take images of the colon. If something is seen that may need to be biopsied, a follow-up colonoscopy will be needed. CT colonography must be done every 5 years.

Tests that mainly find cancer:

  • Guaiac-based fecal occult blood test (gFOBT) and fecal immunochemical test (FIT) are used to find tiny amounts of blood in the stool that could be a sign of cancer or large polyps. People take these tests at home with a kit they receive from their doctor’s office, along with instructions. A positive result will need to be followed up with a colonoscopy. However, many times the cause is a non-cancerous condition, such as ulcers or hemorrhoids. Stool tests like these need to be done every year.

Talk to your doctor about screening

Regular screening is one of the most powerful weapons for preventing colon cancer. If polyps are found during colon and rectal cancer testing, they can usually be removed before they have the chance to turn into cancer. Testing can also result in finding cancer early, when it’s smaller, easier to treat, and more likely to be curable.

If you’re 50 or older, talk to your doctor about which test is right for you and get tested as often as recommended. People at higher risk for colon or rectal cancer because of family history or certain health conditions (such as inflammatory bowel disease) may might need to start screening earlier.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master's-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

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