This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Colonoscopies might beat out root canals as the most reviled commonplace medical procedure that many of us might expect to undergo. Nevertheless, the uncomfortable undertaking is currently one of the best ways to detect early signs of colorectal cancer, a disease that more than 142,000 Americans are diagnosed with each year—and one that kills more than 51,000.
But adults between the ages of 50 and 74 might soon be able to put the dread days of recommended decadal colonoscopies behind them. Researchers announced Thursday early results that indicate their noninvasive test has excellent accuracy in detecting the cancer—as well as more than half of substantial precancerous polyps.
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"This test exceeded our expectations," David Ahlquist, a professor of medicine at the Mayo Clinic and study collaborator, said in a press briefing at the American Association for Cancer Research's Colorectal Cancer conference in Philadelphia. The test, which is being developed by Madison, Wisc.–based company Exact Sciences, looks for telltale signs of cancerous DNA methylation in stool samples.
In a study of some 1,100 individuals, the test had about an 86 percent accuracy rate in detecting cancers that could be removed surgically. It "would be hard," Ahlquist said "to find another non-invasive test that got into that range." Other gentle screening methods, such as fecal blood tests, can detect cancers but usually miss indications of pre-cancerous lesions. The new test also caught more than half (about 64 percent) of sizable precancerous lesions.
And unlike the conventional testing method that relies on small cameras (inserted, via a tube, through the rectum) to detect signs of the cancer, Ahlquist pointed out, the new test is "side-agnostic." Colonoscopies notoriously miss early cancer clues on the right side of the colon because it is farther up in the digestive tract and often less clear during the examination. But because this test relies on a sample of material passing through the system, it detected cancer and pre-cancerous signs regardless of where they were located.
Ahlquist hopes that the new approach will usher in an era of easy, at-home testing where adults might be more willing to undergo the screening (a test kit might be prescribed by a health professional and then sent to a lab for analysis). "We think that user friendliness will enhance compliance," he said.
The test wouldn't banish visual examinations altogether, however. Rather, it might serve as a pre-screening step, only recommending those with positive results to report the clinic for a colonoscopy, Ahlquist explained to Reuters.
The new test currently has a false-positive rate of about 10 percent, but it could end up sending far more in for exams than necessary, Achim Plum, vice president of Epigenomics (a company that makes a blood-based test), told The New York Times.
Although many adults develop polyps, less than 10 percent end up turning into cancer, so a general stool-based test also might pick up on too many non-cancerous growths, Plum suggested. Even so, a pre-screening test would likely cut down on the total number of adults who get (or are recommended to get) more invasive testing—and perhaps encourage a visual screening by a doctor among those who are most at risk for developing a cancerous growth.
Further study of the test will need to be done before it can be submitted for FDA approval.
Image courtesy of iStockphoto/Eraxion