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New Test May Ease Colorectal Cancer Screening

Noninvasive Test May Encourage More Frequent Colorectal Cancer Screening

WebMD Health News

Dec. 22, 2004 -- A new, noninvasive screening test for colorectal cancer may encourage more people to get tested for the deadly and often silent disease.

New research shows that the experimental test, which screens for genetic mutations associated with colorectal cancer found in stool, is more effective at detecting cancers and precancerous growths than the only currently available noninvasive test, fecal occult blood stool testing (FOBT).

While neither of these noninvasive screening tests approaches the detection accuracy of a colonoscopy, researchers say the easy-to-administer test may offer a new alternative for colorectal cancer screening.

"A simple, noninvasive test that detects tumor-specific products with reasonable sensitivity and specificity might overcome barriers to screening among persons who are not willing to have a more invasive test, such as colonoscopy," says researcher Thomas Imperiale, MD, professor of medicine at the Indiana University School of Medicine, in a news release.

Although colorectal cancer is the second leading cause of cancer death among adults and recommendations exist that encourage screening for all adults over 50, researchers say less than 40% of people aged 50 years or older are screened for colorectal cancer.

"There are many reasons why people don't get screened for colon cancer," says Imperiale. "Some individuals do not want colonoscopy because of discomfort, despite conscious sedation, its inconvenience, or its risk for complications; others are unwilling to smear stool samples on a card for the occult blood test every year."

New Option in Colorectal Cancer Screening On the Way

In the study, which appears in the Dec. 23 issue of The New England Journal of Medicine, researchers compared the rates of fecal DNA testing with FOBT in detecting colorectal cancers or precancerous growths (polyps) in more than 2,500 men and women over age 50 considered to be at average risk for colorectal cancer.

Previous studies have shown the fecal DNA testing was effective at detecting cancers and precancerous growths in people at high risk for the disease, but researchers say this study is the first to test fecal DNA detection rates in large numbers of people at average risk.

The fecal DNA test screens for 21 different genetic mutations associated with colorectal cancer found in stool. It requires a single stool sample, which is expelled from the body directly into a container.

The results showed that the stool screening test was four times more sensitive than the FOBT test in detecting invasive colorectal cancers and more than twice as sensitive in detecting precancerous growths.

Researchers say the fecal occult blood test found only 13% of colorectal cancers while the fecal DNA test found 52%, as verified by colonoscopy.

The fecal DNA testing detected 13 cancers that were missed by FOBT, while the FOBT detected one cancer that was missed by the fecal DNA test.

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