New Stool Test Might Aid in Early Detection of Colon
TUESDAY, April 3 (HealthDay News) -- A noninvasive stool test
could help doctors detect early stage colorectal cancer and
precancerous growths, a new study says.
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.
Still, other issues remain, and experts say that the stool-based
test won't replace colonoscopy anytime soon as the best means of
spotting colon polyps or tumors.
"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
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.
The U.S. National Cancer Institute provides more information on
colon and rectal cancer.
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