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The test might help minimize false-positive results and prevent deaths associated with this type of cancer, said researchers at the Mayo Clinic in Rochester, Minn., and Exact Sciences, the company developing the test.
"For now, colonoscopy remains the undisputed winner when it comes to screening for colon cancer," said Dr. Lawrence Cohen, associate clinical professor of gastroenterology at Mount Sinai School of Medicine in New York City. He was not involved in the study.
The research was to be presented Tuesday at the annual meeting of the American Association for Cancer Research (AACR) in Chicago.
The new stool-based screen targets multiple molecular "markers" in stool. Tested in 500 patients who were also undergoing colonoscopy or follow-up care after the detection of colon polyps, researchers found that the screen was highly sensitive to certain critical early cancer screening targets. Unlike other stool-based colon cancer tests, the new test also seemed to be unaffected by patients' medications, sex, race, body mass, lifestyle or family history of colorectal cancer or polyps.
These results mean that "patients don't have to change their lifestyle to have this test," Dr. David Ahlquist, professor of medicine and a consultant in gastroenterology and hepatology at the Mayo Clinic, said in an AACR meeting news release. "That was important from a patient-friendly standpoint for a test like this and could benefit compliance."
The study's authors noted, however, that a patient's age was the one variable that seemed to influence test results. Based on the study's findings, the two markers least vulnerable to age would undergo further test development.
"This test, if broadly applied, should have a very important impact on reducing both the mortality and incidence of colorectal cancer," Ahlquist said. "If we can minimize the false positives, that will reduce the cost of the whole screening program by avoiding unnecessary colonoscopies."
The screening test is currently undergoing FDA validation in a study in the United States and Canada. This study is expected to conclude in the fall.
The Mayo Clinic and Ahlquist reported having a financial interest in the screening technology.
Experts in colon cancer prevention said the test seems to have pros and cons.
"This test offers significant potential to improve upon current stool-based tests as it is unaffected by diet, lifestyle and other important factors which affect current stool-based testing," noted Dr. David Bernstein, chief of the division of gastroenterology at North Shore University Hospital in Manhasset, N.Y.
"The need for colonoscopy, however, would be unlikely to change as this test relies upon specific colon cancer gene markers which may not account for all cases of colon cancer," he added. "This test may be useful in distinguishing low- from high-risk individuals at risk for colon cancer."
For his part, Cohen said the particular gene-based approach used by the Mayo screen is "likely to improve the sensitivity and specificity of this stool DNA test." But he said that stool-based screening still falls short in accurately spotting certain precancerous lesions of the colon compared to colonoscopy.
"An additional challenge for stool testing is cost," Cohen added. "Cost analyses of stool DNA testing have found it to be less cost-effective than any other method of colorectal screening," he said.
Research presented at medical meetings is typically considered preliminary until published in a peer-reviewed journal.
-- Mary Elizabeth Dallas
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