TORONTO — New Canadian guidelines say colonoscopy should not be used for routine screening to detect colorectal cancer in patients with no symptoms or family history of the disease.
The guidelines from the Canadian Task Force on Preventive Health Care strongly recommend that low-risk patients aged 50 to 74 be screened using fecal occult blood tests every two years or sigmoidoscopy every 10 years.
Sigmoidoscopy involves the insertion of a flexible scope to view the lower portion of the colon and rectum rather than the entire tract, as is the case with colonoscopy.
The task force also advises against screening asymptomatic patients age 75-plus because of their reduced life expectancy and the lack of research showing benefit or potential harms of the tests.
Task force member Dr. Scott Klarenbach of the University of Alberta says the guidelines do not apply to high-risk patients who have symptoms or a family history of the disease.
Colorectal cancer is the second most common cause of death from cancer in men and the third leading cause of cancer deaths in women. In 2015, an estimated 25,000 Canadians were diagnosed with colorectal cancer, and approximately 9,300 died from the disease.
"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," said Dr. Maria Bacchus, an internist at the University of Calgary who chaired the guideline working group.
"However, ongoing clinical trials are working to address this research gap," she said.
The new guidelines are based on the latest available research and update the task force's previous 2001 advice, which recommended fecal occult blood testing every one to two years or sigmoidoscopy every five years in asymptomatic adults.
The Canadian guideline is similar to the 2008 U.S. Preventive Services Task Force recommendation that adults aged 50 to 75 should be screened for colorectal cancer using a fecal occult blood test or flexible sigmoidoscopy.
While the U.S. group also recommended colonoscopy, its Canadian counterpart does not believe there is sufficient evidence to support that decision.
The Canadian task force was established to develop clinical practice guidelines for primary-care providers related to a variety of preventive-health issues, based on a systematic analysis of the most recent scientific evidence. The guideline is available at www.canadiantaskforce.ca.
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Sheryl Ubelacker, The Canadian Press