(Reuters Health) - The Canadian Task Force on Preventive Health care recommends that colonoscopy should not be used to screen adults for colon cancer. Instead, they suggest testing for microscopic amounts of blood in the stool.

Colon cancer screening programs aim to identify and remove polyps that can sometimes become cancerous. Currently, all Canadian programs recommend screening using stool tests, with so-called guaiac fecal occult blood testing (gFOBT) or fecal immunochemical testing (FIT).

Today in the journal CMAJ, the Canadian Task Force on Preventive Health Care, an independent panel of clinicians and methodologists, presents its updated recommendations for screening for colon cancer in adults aged 50 years and older who have no symptoms and who are not at a high risk for colon cancer.

Opposition to colonoscopy as a primary screening test for colon cancer stems from the lack of evidence showing it to be any better than other screening methods, the Task Force says.

The task force makes a strong recommendation for screening adults aged 60 to 74 with FOBT or FIT every 2 years or flexible sigmoidoscopy every 10 years, and they make a weak recommendation for using a similar approach in adults aged 50 to 59.

The task force recommends against screening adults aged 75 years and older because existing studies do not demonstrate an improvement in colon cancer mortality from such screening.

These recommendations differ from those published by the U.S. Preventive Services Task Force in 2008, which support the use of FOBT, flexible sigmoidoscopy, or colonoscopy for colon cancer screening in adults aged 50-75.

“Regardless of age, primary care providers should discuss the most appropriate choice of test with patients who are interested in screening, considering patient values and preferences as well as local test availability,” the recommendations conclude.

Dr. Robert Smith, American Cancer Society (ACS) Vice President for Cancer Screening, Atlanta, Georgia, told Reuters Health by email, “In the U.S., the advantage of colonoscopy was judged to be clear in spite of the absence of data from a prospective randomized controlled trial, and early on the ACS and U.S. Multi-Society Task Force endorsed screening colonoscopy every 10 years, and eventually the USPSTF did also. However, the U.S. guidelines also see greater advantage from annual stool testing vs. stool testing every other year.”

“New data also show very clearly that a substantial fraction of adults are not willing to undergo colonoscopy and thus recommendations to get a colonoscopy in this group will go unheeded,” Smith said. “The data also show that many of these adults will accept stool testing, and thus achieving high rates of colorectal cancer screening in the practice setting requires providing at least the option for colonoscopy or, ideally, a high sensitivity FIT.”

Smith concluded, “We have a saying….the best test for colorectal cancer screening is the one that gets done.”

The Canadian Task Force on Preventive Health Care did not respond to a request for comments.

SOURCE: bit.ly/1QVLsIX CMAJ, online February 22, 2016.