Wednesday, November 2, 2022

About the Gold Standard Colonoscopy Study


Environmental & Science Education, STEM, Health, Medicine

Ed Hessler

You've probably seen  reporting on a gold standard trial which put colonoscopy screening to the test. Eighty thousand participants (ages 55 to 64) from Poland, Norway and Sweden were invited to participate. A random sample of 28,000 were chosen of which 42% agreed to colonoscopies during that period. The rest received their usual care which did not include routine colonoscopies. They were followed for ten years and data were collected on colon cancer diagnoses, deaths, and deaths from other causes.

Angus Chen has written a thorough report for STAT News which if you are at all interested in the findings and interpretations is must reading. And if you are of a certain age you may want to. I do not do it justice here as I pick and choose.

According to Chen,  "the trial’s primary analysis found that colonoscopy only cut colon cancer risk by roughly a fifth, far below past estimates of the test’s efficacy, and didn’t provide any significant reduction in colon cancer mortality." Many thought that colonoscopy would do better because it is widely heralded and promoted, including clever PSA's, many aimed at men, traditionally recalcitrant to visiting a doctor much less receiving a colonoscopy. I recall one opening with "Real Men Wear Gowns."

Gastroenterologist Dr. Samir Gupta, University of California, San Diego and the Veterans Administration showed surprise, telling Chen, while stressing the point,  "that the study does not invalidate colonoscopies as a useful screening tool. Colonoscopies are still a good test but it may be time to reevaluate their standing as the gold standard of colon cancer screens. “This study provides clear data that it’s not as simple as saying, "‘Colonoscopy is the most sensitive test, and therefore it is the best.’ It still prevented cancers.'”

As you know the intestinal probe includes a camera and when pre-cancerous polyps, known as adenomas, it’s promptly removed, thus nipping the cancer before it spreads." The results of studies of this intervention showed a large reduction "in the incidence and mortality from colon cancer."  None of these previous studies was large or randomized.

When asked about the study, Dr. Jason Dominitz, "the executive director of the National Gastroenterology and Hepatology program at the VA," told Chen that "nuances abound in interpreting the data. For one, a minority of participants who were invited to colonoscopy actually showed up for one. That may have diluted the observed benefits of colonoscopy in the study. Cancer treatment has also progressed over the last couple of decades, too, and the study only had 10 years of follow-up thus far, both of which would make it harder to see a mortality benefit from the screen. 'They’re doing a 15-year follow, and I would expect to see a significant reduction in cancer mortality in the long term. Time will tell.'”

A less robust "secondary analysis also offers another silver lining," according to Dr. Gupta." When the investigators compared just the 42% of participants in the invited group who actually showed up for a colonoscopy to the control group, they saw about a 30% reduction in colon cancer risk and a 50% reduction in colon cancer death. 'That adds to a bunch of observational study data that suggests exposing people to colonoscopy can reduce risk of developing and dying of colon cancer.'” 

Continuing, University of Oslo study leader Dr. Michael Bretthauer said that "colonoscopy screening’s true benefit may lie somewhere in between the primary and secondary analyses in his study. 'You may reduce your risk of getting colorectal cancer by 20 to 30% if you get a colonoscopy.' Bretthauer said. That brings it more in line with the other main colorectal cancer tests, which analyze feces for signs of cancer, either abnormal DNA or blood, and can be taken at home.

"That raises an important point for policymakers." Bretthauer added. "Colonoscopy is more expensive, more time-intensive, and more unpleasant in preparation for patients. Many European countries balked at putting public health dollars towards a large, expensive program, he said, when the fecal testing was cheaper, easier, and had greater uptake in certain studies (linked in Chen's article). “'Now, the European approach makes much more sense. It’s not only cheaper, but maybe equally effective.

The original research was published in the New England Journal of Medicine where you may read a free preview - abstract, background, methods, results, conclusions, i.e., not the entire article or many details unless you are a subscriber or have an account allowing access.

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