Colorectal ​Cancer:​ Screening

If a colorectal cancer screening isn’t your idea of a good time, you’re not alone. That said, screenings are very important. Finding cancer early can make it much easier to treat. Screening can even prevent colorectal cancer. A healthcare provider can find and remove growths called polyps in the colon or rectum. Taking them out early can keep polyps from turning into cancer.

How does screening work?

There are many tests that can screen for colorectal cancer, described below. Talk with your provider about what option is best for you.

Visual screenings

These tests let your healthcare provider look inside your colon and rectum. They check for abnormal areas that could be cancer or polyps. These tests are done in a healthcare facility. Your provider will give you special instructions to follow before the test.

  • Colonoscopy. This test looks at your rectum and entire colon. You will get medicine to let you comfortably sleep during the procedure. For the test, the provider inserts a flexible thin tube into your rectum and your colon. This tube has a light and a tiny video camera. Your provider looks for polyps or other abnormal areas. These can be removed and sent for testing. A colonoscopy is the one test that shows your provider your whole colon and rectum. Because of this, they’re often used if other tests find something your provider needs a better look at.
  • Flexible sigmoidoscopy. This test is very similar to a colonoscopy. It also uses a small tube with a tiny video camera. Your healthcare provider inserts the short, flexible, thin tube into your rectum. It looks at your rectum and the lower part of your colon only. Just like with a colonoscopy, your provider checks for polyps or other abnormal areas that can be removed and sent for testing. But a flexible sigmoidoscopy looks at less of your colon than a colonoscopy.
  • Virtual colonoscopy (CT colonography). This test is a special type of CT (computed tomography) scan of your entire colon and rectum. A CT scan takes detailed X-ray pictures. A computer takes these images and combines them to create a 3-D picture. This lets the provider look for polyps or cancer. These polyps and abnormal areas of your rectum and colon cannot be removed with this type of test.

Stool-based screenings

There are other tests that look for signs of colorectal cancer in your stool. However, they are less likely to find polyps. One benefit to these tests is that you can take them at home. But you have to do them more often than the visual tests above.

  • Guiac-based fecal occult blood test (gFOBT) or fecal immunochemical test (FIT). These tests look for hidden blood in the stool. Blood vessels in cancers and polyps are easily broken during a bowel movement. This may cause blood to show up in your stool. For these tests, you collect a small amount of stool with a brush or wooden applicator. Then you smear it on a special card that detects blood. You often need to repeat this a few times. Your provider will tell you where to send the cards.
  • Stool DNA test ( also called multi-targeted stool DNA test or mt-sDNA). This test also examines your stool. It checks for DNA changes in cells in the stool that might be signs of cancer. It also looks for hidden blood. You collect an entire bowel movement for this test. This is done using a special container you put in the toilet. Then, you’ll send the sample off for testing.

Blood tests

There are blood tests available that look for signs of colorectal cancer or pre-cancerous polyps. A sample of your blood is taken in a clinic and tested in a lab. You don't need to do any bowel prep before this test. If you have abnormal results, you will likely need a colonoscopy.

When should I get screened?

The American Cancer Society and U.S. Preventive Services Task Force advise people at an average risk for colorectal cancer to start screening at age 45. You may need to start screening earlier if you’re at a higher risk. Your provider can help you determine if you are average or higher risk.

How often do I need to be screened?

How often screening tests are done varies from person to person. It will depend on the test, your health history, and your risk factors.

Screening tests for those at an average risk for colorectal cancer can include:

  • A colonoscopy every 10 years

  • A flexible sigmoidoscopy every 5 years (or every 10 years with yearly FIT stool test)

  • A virtual colonoscopy every 5 years

  • An gFOBT or FIT every year

  • A stool DNA test every 3 years

How do I tell if I’m at a higher risk for colorectal cancer?

You may have a higher risk if you have:

  • A personal or family history of colorectal cancer

  • Certain types of polyps found on previous tests

  • Inherited syndromes like:

    • Polyposis syndromes like familial adenomatous polyposis (FAP)
    • Lynch syndrome (also called hereditary non-polyposis cancer (HNPCC)

  • A personal history of inflammatory bowel disease like Crohn's or ulcerative colitis

  • Radiation to the belly (abdomen) or pelvis as part of a past treatment

People at a higher risk may start screening earlier. They may need more frequent screenings, too

Talk with your healthcare provider

It can be scary to have conversations about your risks for cancer. But it’s important to know your risk levels.

Talk with your provider. They can help you figure out:

  • When you should start screening

  • Which tests might be right for you

  • Which tests are covered by your health insurance

Remember that you’re not alone. Your provider can help you navigate each step of the screening process. Colorectal cancer tests may not be fun, but keep in mind: Early detection is a powerful and important tool in fighting cancer.