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Canadian guideline opposes colonoscopy for routine screening of CRC
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The Canadian Task Force on Preventive Health Care has released an updated guideline on screening for colorectal cancer, which recommends that instead of colonoscopy, fecal occult blood testing every 2 years or flexible sigmoidoscopy every 10 years should be used for adults aged 50 to 74 years who are asymptomatic and not at high risk for colorectal cancer.
“Although colonoscopy may offer clinical benefits that are similar to or greater than those associated with flexible sigmoidoscopy, direct evidence of its efficacy from randomized controlled trials in comparison to the other screening tests ... is presently lacking; however, ongoing clinical trials are working to address this research gap,” Maria Bacchus, MD, chair of the guideline working group and a general internist in the department of medicine at the University of Calgary, Alberta, said in a press release. “Wait lists for colonoscopy remain long in Canada and have increased over the years.”
As technology and practice have undergone major changes since the last version of the guideline was published in 2001, the task force has updated recommendations on screening tests, screening intervals and ages to start and stop screening, based on the most recent data.
“These recommendations … do not apply to those with previous [CRC] or polyps, inflammatory bowel disease, signs or symptoms of [CRC], history of [CRC] in one or more first-degree relatives, or adults with hereditary syndromes predisposing to [CRC],” the authors wrote.
The task force strongly recommends adults aged 60 to 74 years should be screened for CRC using guaiac fecal occult blood testing (gFOBT) or fecal immunochemical testing (FIT) every 2 years or flexible sigmoidoscopy every 10 years. They also weakly recommend screening adults aged 50 to 59 years using the same methods at the same intervals, as a lower absolute benefit is expected from screening in this age group.
These recommendations are based on data from a systematic review of four randomized controlled trials of gFOBT, one of FIT and four of flexible sigmoidoscopy. Among individuals aged 45 to 80 years, gFOBT reduced CRC-related mortality (RR = 0.82; 95% CI, 0.73-0.92) and late-stage CRC incidence (RR = 0.92; 95% CI, 0.85-0.99), and among individuals aged 55 to 74 years, flexible sigmoidoscopy reduced CRC-related mortality (RR = 0.74; 95% CI, 0.67-0.82) and late-stage CRC incidence (RR = 0.73; 95% CI, 0.66-0.82). Additional studies show FIT can be substituted for gFOBT for screening.
The task force also recommends against screening adults aged 75 years and older, but this is based on low-quality evidence; therefore, they wrote that individuals in this age group “should discuss screening with their primary care provider to determine their most appropriate screening option based on their personal values and preferences.”
Finally, the task force recommends against using colonoscopy as a primary screening test. “This recommendation is weak, given the level of uncertainty over the effectiveness and harms of colonoscopy as screening test,” the authors wrote. “The harms include intestinal perforation (0.05% of patients), minor bleeding (0.08%), major bleeding requiring hospital admission (0.1%) and death (0.002%).”
The task force concluded that primary care practitioners should offer screening to all patients aged 60 to 74 years, and should discuss the harms and benefits of screening and patient preferences in other age groups and in patients interested in screening regardless of age. – by Adam Leitenberger
Disclosure: The researchers report no relevant financial disclosures.
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