Dennis J. Ahnen, MD, AGAF

Dennis J. Ahnen, MD, AGAF

CRC screening guidelines vary around the world. The U.S. is one of the only countries, for example, that relies heavily on colonoscopies for CRC screening in average-risk populations. Other countries tend to rely on less expensive and less invasive screening technologies for average-risk screening.

“There are strikingly divergent points of view on colorectal cancer screening in different countries and regions of the world,” said Dennis J. Ahnen, MD, AGAF, professor emeritus at the University of Colorado School of Medicine and director of the genetics clinic at Gastroenterology of the Rockies, Denver. “It’s not just the differences in opinion and guidelines that are interesting and important, but also the rationale behind these divergent guidelines.”

Worldwide variations in CRC screening guidelines will be examined during Tuesday’s AGA Clinical Symposium U.S. and International Colorectal Cancer Screening Guidelines. The reasoning behind different CRC screening guidelines is a combination of philosophical and resource-utilization approaches, Dr. Ahnen said.

The U.S. Preventive Services Task Force (USPSTF) sparked a bit of international controversy when it published new guidelines in 2016. Those guidelines open CRC screening to any of five different technologies at different intervals: colonoscopy, flexible sigmoidoscopy, high-sensitivity fecal occult blood tests (FOBT), flexible sigmoidoscopy plus FOBT, CT colonography or the combined stool DNA/testing. The guidelines discuss the strengths and weaknesses of each modality, but do not rank or recommend specific methods, Dr. Ahnen noted.

“In the absence of randomized controlled trial data, the USPSTF used predictive modeling to compare the effectiveness of these screening options and concluded that there was not convincing evidence that one test was superior to the others,” he said.

Other than the U.S., few countries routinely perform colonoscopies for first-line screening in average-risk populations. Most countries that have a national screening program use fecal occult blood testing and/or flexible sigmoidoscopy.

Canada and Europe are awaiting the results of randomized controlled trials before deciding whether to add colonoscopies to the list of acceptable first-line screening techniques for average-risk populations, Dr. Ahnen said, but those results won’t be available for some time.

“Different conclusions about routine use of colonoscopy as a CRC screening test are also based on the resources available,” he said. “Many countries lack sufficient endoscopists for population-based screening and have chosen not to devote the resources to build capacity until there’s better evidence to warrant the higher expense.”

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