Canadian Task Force Recommends Stool Testing Over Colonoscopy for Screening

By Will Boggs MD

February 23, 2016

NEW YORK (Reuters Health) - The Canadian Task Force on Preventive Health Care (CTFPHC) recommends against colonoscopy for colorectal cancer (CRC) screening of asymptomatic adults, favoring instead guaiac fecal occult blood testing (gFOBT), fecal immunochemical testing (FIT), or flexible sigmoidoscopy.

The CTFPHC updates its 2001 recommendations based on the most recent data available in its February 22nd CMAJ online report.

For adults aged 60 to 74, the task force strongly recommends screening for CRC with gFOBT or FIT every two years or flexible sigmoidoscopy every 10 years, based on moderate-quality evidence. A weak recommendation based on moderate-quality evidence supports similar screening of adults aged 50 to 59.

The task force weakly recommends against screening adults aged 75 years and older for CRC based on low-quality evidence showing no improvement in CRC mortality or morbidity in this age group.

The weak recommendation against colonoscopy as a primary screening test for CRC is also based on low-quality evidence. "Although colonoscopy may offer clinical benefits that are similar to or greater than those associated with flexible sigmoidoscopy, direct evidence of its efficacy in comparison with the other screening tests (in particular FIT) is lacking," the authors note.

They also cite lengthy wait lists for colonoscopy and insufficient gastroenterologists in Canada as arguments against routine colonoscopy for CRC screening.

"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, "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, consistent with the stronger data from the Minnesota Trial."

"We're still learning about long term outcomes associated with flexible sigmoidoscopy, but it should be recognized that deaths prevented are limited to the cancers that arose in the distal colon," he explained. "That is one reason why it has fallen out of favor in the U.S., along with weak incentives for its use in the primary care setting."

"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," Dr. 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."

"If a practice is still using the old Hemoccult tests, they should stop and replace them with either a high sensitivity guaiac test (i.e., Hemoccult SENSA) or a high sensitivity FIT," he said. "FIT is more patient friendly, more likely to be completed, and tends to have overall better accuracy. High sensitivity stool testing should not be judged as an inferior test to colonoscopy, especially for a patient who will not get screened if colonoscopy is the only option."

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

The CTFPHC did not respond to a request for comments.


CMAJ 2016.