Colorectal Cancer Screening: Which Test is Right for Me?


Colorectal cancer is one of the most common cancers in both men and women.  It is also considered one of the more preventable cancers due to the effectiveness of screening. But which screening option is right for you?

Charles Fuchs, MD, MPH, and Jeffrey Meyerhardt, MD, MPH, of the Gastrointestinal Cancer Center at Dana-Farber/Brigham and Women's Cancer Center

Charles Fuchs, MD, MPH, and Jeffrey Meyerhardt, MD, MPH, of Dana-Farber’s Center for Gastrointestinal Oncology.

“There are several different appropriate methods for colorectal cancer screening,” explains Jeffrey Meyerhardt, MD, MPH, clinical director of the Center for Gastrointestinal Oncology at Dana-Farber/Brigham and Women’s Cancer Center. “Some of the tests are more sensitive, but more complicated.”

  • Fecal occult blood testing. One type of screening is fecal occult blood testing, where patients complete a set of stool samples at home and return them to the doctor to test for evidence of microscopic blood. This test has been proven to decrease the incidence of colon and rectal cancers and mortality, and should be done annually.

While fecal occult blood testing is the most convenient method, Meyerhardt recommends the colonoscopy for most patients because of its sensitivity.

  • Colonoscopy. “The colonoscopy is best able to detect polyps, which are precursors to colorectal cancers, as well as cancer itself,” says Meyerhardt. “Fecal occult blood testing is only considered sensitive for cancer, not polyps, the precursor for most cancers, making it much less comprehensive than a colonoscopy.”

Colonoscopies are slightly more complicated, and require a liquid diet the day prior to screening, some preparation to clean out the colon and rectum, and an outpatient procedure. If you have a clean colonoscopy, without any concerning polyps or cancer, you need only be screened every 8-10 years. If your physician finds polyps during your colonoscopy, the time between screenings will depend on the size, location, and characteristics of any polyps.

  • Sigmoidoscopy and barium enema. Other screening options include a sigmoidoscopy, which examines the rectum and lower colon for polyps and needs to be completed every five years, and a barium enema, which is a series of x-rays of the lower gastrointestinal tract. While sigmoidoscopies or fecal occult blood tests are acceptable colonoscopy substitutes for those with no risk factors or symptoms of colon or rectal cancer, barium enemas may miss small polyps and only detect between 30 and 50 percent of the cancers that a standard colonoscopy can find.

“All of the screening tests carry some risks, and the more sensitive the test, the higher the risk,” says Meyerhardt. “During a colonoscopy, there’s a very small risk of a perforation of the bowel, bleeding, or infection. The biggest risk of fecal occult blood testing and other screening measures is missing something, which could turn out to be much more serious.”

All adults aged 50 and older should be regularly tested for colon and rectal cancers. If you have certain risk factors, such as a family history of colon or rectal cancer, Crohn’s disease, ulcerative colitis, or a history of polyps, testing should be considered earlier than age 50. For example, those who have a history of colon or rectal cancer in an immediate family member should begin testing 10 years prior to the age of their family member’s diagnosis. For example, if a sibling or parent was diagnosed at 50, your first screening should take place at the age of 40. For all individuals, the time between testing depends on screening type and risk factors. Discuss the right time for you to start screening for colorectal cancer with your doctor.


  1. Can a virtual CT scan of the colon replace a colonoscopy? How and when should this test be used?

    • Dear Caren —

      Virtual CT scans (or CT colonograph) is another test that the American Cancer Society considers an appropriate test to find polyps and cancer. It is a bit less sensitive than a colonoscopy. It requires a patient to still prep like a colonoscopy and if there is anything abnormal found, the patient then needs to undergo a colonoscopy. As such, if a patient is considering doing a virtual CT scan, you should make sure you are doing it in a center that can immediately bring you to colonoscopy if anything abnormal is found. Otherwise, you will have to do a full bowel prep twice.

      I hope this is helpful and wish you the best.

  2. How about the Cologuard dna test? Is this a valid predictor?

  3. Dear Philip —
    Thank you for your question and for reading Insight. We spoke with one of our experts, who provided this response:

    The Cologuard is an FDA-approved screening test for colorectal cancer. It looks for changes in DNA in stool that could indicate that an individual has colorectal cancer. Its main limitation is that it can only detect early cancers — it cannot detect pre-cancerous lesions and thus PREVENT colon cancer (whereas a colonoscopy can). However, the bottom line is that it’s important that people just get screened — so if someone is more willing to get a stool-based test like the Cologuard over a colonoscopy, then that is better than no screening at all.

    We hope this is helpful. Wishing you all the best.

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