Know the guidelines: When to start colorectal cancer screening?

March is colorectal cancer awareness month, so there is no better way to kick it off than a review of the current screening guidelines for colorectal cancer! There are at least three different major societies issuing slightly different guidelines on colon cancer screening. In this article, I will try to blend the different guidelines together to make a practical basic summary for the practicing physician.

Just a word about screening tests in general: Screening by definition is the act of looking for a disease in a person with no symptoms. Thus, if a patient is having signs or symptoms of a potential colorectal cancer (such as rectal bleeding, change in the bowel habits, abdominal pain, iron-deficient anemia, unintentional weight loss, etc.) then they are not in the screening category any longer. Also, the whole purpose of screening is to pick up a problem early, with the theory being that fixing a little problem is easy, rather then waiting for a little problem to grow into a big problem that may cause loss of life or other bad outcomes. So using the example of colon cancer, we do screening colonoscopy to detect and remove colon polyps (which are the precursors of colon cancer) and thus reduce the risk of developing colorectal cancer in the future.

There are several different tests that satisfy the “colorectal cancer screening” checkbox. In order to keep this information simple and practical, I will mirror the American College of Gastroenterology (ACG) guidelines in recommending a preferred testing strategy and then some alternatives. This is easier, quicker, and may lead to better outcomes than offering patients a menu of various “equal” screening choices to pick from.

If there is one take-home message for colorectal cancer screening it is this:

Start screening most people at age 50. Colonoscopy is the preferred screening test. 

What if someone cannot have a colonoscopy for medical reasons, or patient preference, or if the test is not easily available? Secondary screening tests that are acceptable (from most preferred to least preferred) are the following:

  • Flexible sigmoidoscopy every 5 years
  • CT colonography (“virtual colonoscopy”) every 5 years
  • Fecal immunochemical test (FIT) every 1 year
  • Hemoccult Sensa test every 1 year
  • Fecal DNA testing every 3 years
  • (Of note, if any of the above alternative screening tests are positive, then a full colonoscopy needs to be done to confirm and treat the positive finding.)

What about if there is a family history of colorectal cancer?

  • Average-risk guidelines still apply to people with only one first-degree relative with colorectal cancer diagnosed at age 60 or later.
  • High-risk guidelines apply to people with one first degree relative with colorectal cancer diagnosed younger than age 60, or with two first-degree relatives diagnosed at any age:
    • Screening test should be colonoscopy.
    • Start screening at age 40, or 10 years younger than the age of diagnosis of the relative (whichever is earlier).
    • Repeat screening colonoscopy every 5 years.

What about if there is a family history of colon polyps? 

  • Use the high-risk guidelines above if there is a family history of an advanced adenoma (defined as any adenoma >1 cm in size, or with high-grade dysplasia, or villous elements). An advanced adenoma is equivalent to a cancer in terms of the screening guidelines.
  • For other adenomas, or non-adenomatous polyps, use average-risk guidelines.

Special populations:

The ACG is unique in recommending that black patients should be offered screening starting at age 45. The rationale for this is that colorectal cancer has a higher mortality in black patients, therefore by detecting it earlier more lives may be saved. The ACG notes this is a weaker strength recommendation because there is a lack of quality evidence that this strategy actually works.

Women should be screened the same way as men, starting at the same age. It is well-known that men develop polyps more commonly and at an earlier age than women, however a significant percentage of women also have colon polyps found at age 50. Therefore, the guidelines are the same for men and women.

Inflammatory bowel disease (ulcerative colitis or Crohn’s disease) patients have their own separate guidelines and therefore these guidelines do not apply. Same goes for patients with hereditary colon cancer syndromes such as FAP and HNPCC (Lynch syndrome).

Obesity and cigarette smoking are the two consistent modifiable risk factors for developing colon cancer in general, and also increase the risk of developing colorectal cancer at an earlier age. Other studies have identified heavy consumption of red meat or alcohol as similar risk factors for cancer development. The current guidelines state that there is not enough evidence to support more aggressive screening protocols in these patients, however the option to offer screening earlier is best left to the doctor and individual patient.

Maybe you should think about screening me early?

Maybe you should think about screening me early?

But what about the stool guaiac test? My doctor does a rectal exam every year during my annual physical and tells me there is no blood in my stool. Do I still need a screening colonoscopy?

Yes! “The ACG supports the joint guideline recommendation that older guaiac-based fecal occult blood testing be abandoned as a method for CRC screening” (Rex DK, et al. 2009).

In conclusion, all otherwise healthy patients should begin colorectal cancer screening at age 50. Black patients should be offered screening earlier, at age 45. Colonoscopy is the best screening test currently available. If colonoscopy cannot or will not be done, there are plenty of alternative screening tests. Remember that any screening for colorectal cancer is better than no screening at all.  

Go to the next post in this series: How often do you need to repeat a negative colonoscopy?


American Cancer Society recommendations for colorectal cancer early detection: revised 2/1/2016 (online)

Rex DK, Johnson DA, Anderson JC, et al. American College of Gastroenterology guidelines for colorectal cancer screening 2008. Am J Gastroenterol 2009;104:739-50.

USPSTF final recommendation statement: Colorectal cancer: Screening, October 2008 (online).

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