An experimental, noninvasive test detects more than 9 out of 10 cases of colorectal cancer, according to a new report.

If larger studies confirm the effectiveness of the screen, which looks for abnormal DNA in a stool sample, it may become an appealing option for people who are reluctant to undergo invasive tests to detect colon cancer and precancerous growths called polyps, the study's lead author said in a press conference Tuesday.

We believe that this test has the promise to reduce many of the lives needlessly lost by this very common malignancy, and change the way we screen for colorectal cancer,'' said Dr. David A. Ahlquist, of the Mayo Clinic in Rochester, Minnesota.

Ahlquist said that the new screen would never replace the ''gold standard'' for detecting colon cancer, colonoscopy, which detects virtually all cases of colorectal cancer. People at high risk of colorectal cancer should probably still undergo colonoscopy, he explained.

But for people who have a lower risk, the new noninvasive test may be a good option, according to Ahlquist. He noted that people who are reluctant to undergo invasive testing like colonoscopy or a less extensive test called flexible sigmoidoscopy might be more willing to have the new screen. And although the screen needs to be studied more, it appears to be considerably more accurate than fecal occult blood testing, a screen that looks for blood in the stool.

The experimental screen, which was tested by investigators at Mayo and at EXACT Laboratories in Maynard, Massachusetts, measures abnormal DNA that is shed from the lining of colorectal polyps and tumors, Ahlquist explained. To test how well the screen works, the researchers tested it on 22 people with colorectal cancer, 11 people with polyps and 28 healthy people.

Writing in the November issue of the journal Gastroenterology, Ahlquist and his colleagues report that the test detected cancer in 20 out of 22 people with cancer, an accuracy rate of 91%. And the DNA testing detected 73% to 82% of precancerous polyps, according to the report. In contrast, conventional fecal occult blood testing did not detect any polyps. The researchers also note that the new test did not produce any false-positive results in patients who did not have cancer or polyps.

Ahlquist noted that 60,000 Americans die from colorectal cancer each year, even though it is almost always curable if detected early enough. And if polyps are detected before they become malignant, colorectal cancer can almost always be prevented, he said.

The new test, since it is noninvasive, may be more appealing to many people, the Mayo researcher said. The test is also patient-friendly because it does not require people to restrict their diet or medications in any way, he noted. In addition, unlike flexible sigmoidoscopy, which only examines the lower half of the colon, the EXACT test detects polyps and tumors throughout the colon, Ahlquist explained.

Depending on the results of larger studies testing the EXACT screen, the test will not be available for at least 2 to 3 years, Ahlquist said. The cost of the test has not been determined, although by reducing the need for colonoscopies in many cases, which can cost more than $1,000, the test may end up saving healthcare dollars, Ahlquist said.

(From Reuters Health)