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Colorectal cancer is one of the leading causes of cancer deaths in American
men and women. Fortunately, through regular screenings, it is one of the most
preventable cancers.
Traditional screening tests include flexible sigmoidoscopy, colonoscopy and
fecal occult blood tests. Unfortunately, at least 40 percent of eligible
Americans do not undergo recommended screenings. Part of the reason is the need
for a bowel cleanse before a colonoscopy and dietary restrictions before fecal
occult blood testing. Consumers would enthusiastically welcome the development
of newer, noninvasive methods of screening.
"One of the latest—and noninvasive—methods is a stool DNA test that
might become available later this year," says Carol Burke, M.D., director
of the Cleveland Clinic’s Center for Colon Polyps and Cancer Prevention.
New DNA test
The new DNA test works by detecting genetic mutations in the stool. Genetic
material, called DNA, is present in every cell of the body, including the cells
lining the colon, says Dr. Burke. Normal colon cells and their genetic material
are passed into/in bowel movements every day. When a colorectal polyp or cancer
develops, abnormalities (or mutations) occur in the genetic material of the
colon’s cells. "The mutations present in the polyp or cancer can be
detected by laboratory analysis of the stool," she says.
Stool DNA testing can identify a number of common colon polyp and cancer
mutations. The stool test is noninvasive and requires no specialized diet or
avoidance of medications. "The test is straightforward," explains Dr.
Burke. "A stool sample is mailed to the laboratory, where it is tested for
mutations. If mutations are found, a colonoscopy is warranted."
High accuracy rates
In the small studies performed so far, results show that the test has a 75
percent accuracy of finding mutations present in a cancer. The accuracy to
detect polyps is between 60 percent and 70 percent.
Currently, two large trials involving about 10,000 patients are in progress,
and the results of one of them should be available within the year. "If
these large trials confirm the accuracy of the DNA stool test for
screening," says Dr. Burke, "we can make a big impact on the burden of
colorectal cancer in this country."
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