Unlike U.S., Canada Says Colonoscopy Isn't Gold Standard

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The Canadian Task Force on Preventive Health recently published its new recommendations in CMAJ, coming out against the use of colonoscopies for colorectal cancer screening in low-risk individuals.

Colonoscopy via Shutterstock Colonoscopy via Shutterstock

In the United States, a colonoscopy is considered the gold standard for screening and surveillance of colon cancer. The recommendations for colorectal screening come from two major groups, the United States Preventive Services Task Force, which is an independent body of experts, and from the Multi-Society Task Force.

The USPSTF's recommendations, last updated in 2008 (USPSTF has a draft update on its website), lists three different options for screening in average risk individuals age 50 to 75:

  • Annual fecal occult blood testing (FOBT) with a sensitive test
  • Flexible sigmoidoscopy every five years with sensitive FOBT every three years
  • Colonoscopy every 10 years

The Multi-Society Task Force, or MSTF, makes joint recommendations with the American Cancer Society and the American College of Radiology, which offers two additional test options: computed tomographic colonography (CTC) and fecal DNA testing.

The Canadian counterpart to these agencies, the Canadian Task Force on Preventive Health Care, is an independent panel of experts in collaboration with the Public Health Agency of Canada and the National Colorectal Cancer Screening Network.

Its recommendations are similar to the 2008 USPSTF with one major exception. In a paper published in the journal CMAJ, the agency recommended against the use of colonoscopy as a screening tool for the detection of colon cancer in average risk individuals aged 50-74, and instead to use stool-based tests that check for occult bleeding.

This recommendation is an update from their 2001 guidelines and it asserts that it is based on the most recent available literature. The reason for the change is that there are no randomized controlled trials (RCTs) that report a mortality benefit of screening colonoscopy (or of CT colonography, barium enema, digital rectal exam or fecal DNA testing).

There are data from RCTs, however, that do show screening for colorectal cancer (or CRC) with FOBT or flexible sigmoidoscopy, reduces the incidence of late-stage CRC and CRC mortality.

These recommendations are geared to provide a guide for primary care providers in treating those individuals who are low-risk meaning asymptomatic, no family history of colon cancer, or any other condition that would predispose them to colon cancer.

Regardless of what the guidelines state, it is up to the clinician to discuss the best form of screening that is in line with what the patient wants, and the availability of the screening modality. As Dr. Robert Smith, Vice President of Cancer Screening for the American Cancer Society, told Reuters, ¦the best test for colorectal cancer screening is the one that gets done.

And that is essentially one of the most important aspects of screening for disease. Screening rates for CRC, although rising in the U.S. over the past few years, are generally below national targets. In 2012, 65.1 percent of adults between ages 50 and 75 years were up-to-date with CRC screening and 27.7 percent had never been screened. The individuals who are most frequently not current are the non-white, less educated, uninsured, without a consistent source of care half of whom fare the worst regarding CRC outcomes.