By Elizabeth Armstrong Moore

The new DNA stool test is currently being reviewed for approval by the FDA.

(Credit: Exact Sciences)

Last year alone, almost 50,000 Americans died of colon cancer, and nearly 150,000 new cases were discovered. In fact, it’s the third most common cancer in the US, according to the American Cancer Society. And yet one in every three qualifying Americans doesn’t follow colonoscopy guidelines: getting one at age 50 and every decade thereafter.

There may be many factors at play behind so many people not undergoing the procedure, but even for those who simply feel squeamish about it, it’s hard to blame them. Colonoscopies are invasive, uncomfortable, and at least for some, downright embarrassing.

Soon, however, the millions of adults who forego the colon cancer screening test may have a noninvasive, at-home alternative: a DNA stool test. While it’s not as reliable as a colonoscopy, new research published this week in the New England Journal of Medicine finds that the test, which checks for blood and abnormal DNA, is 92 percent accurate.

The test isn’t yet approved by the Food and Drug Administration, and the research, which comes from the Icahn school of Medicine at Mount Sinai in New York, shows that it isn’t perfect. “But neither is a colonoscopy,” study co-author Dr. Steven Itzkowitz tells HealthDay. “I don’t think we’re saying that this test should be done as a replacement for a colonoscopy, but rather as an adjunct. Certainly if a person who does this test comes out with a positive reading then they will need to do a colonoscopy afterwards to confirm it.”

The research, which was funded by Exact Sciences Corp., the makers of the test, screened nearly 10,000 men and women aged 50 and older for colon cancer and precancerous polyps at 90 sites across the US and Canada. They used three screening methods: the new DNA test, traditional colonoscopies, and a commercially available fecal test (FIT).

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The colonoscopy found colon cancer in 65 patients and precancerous lesions in 757. The DNA test caught 60 of those 65, better than the 48 found using the FIT test. As for precancerous lesions, the stool sample tests were far less accurate — the DNA test found only 42 percent of cases, while FIT found even fewer, just 24 percent.

The DNA test was also more likely to give false positive results than either the FIT test or a colonoscopy. Still, researchers say that testing DNA and blood in stool samples may come with benefits over colonoscopies: It was quite good at finding certain advanced-stage polyps — ones that are flat and harder to pick up via colonoscopy.

Given the mixed findings, it’s safe to say that, should the DNA stool test go to market, those who opt for it should consider following up with a colonoscopy, or at least know the risks of relying solely on the at-home test.

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