Experimental Test for Colon Cancer Is Painless, Faster
Instead of measuring blood in stool, as the fecal blood test does, the new test measures DNA alterations in the stool associated with colorectal cancer and precancerous polyps. It actually is easier for the patient than the existing fecal test, because only one stool sample is required instead of three. If the test is widely adopted, then it could eliminate the need for both the fecal blood test and sigmoidoscopy, Ahlquist says.
The study results, published in the recent issue of Gastroenterology, showed that the test detected 91% of colorectal cancers and 82% of polyps over 1 cm in size. Fecal occult blood testing detected none of the polyps.
The researchers recently received a $4.9 million grant from the National Cancer Institute to conduct a three-year, multicenter clinical trial comparing the DNA screening method to existing testing methods. That trial is scheduled to begin in January of next year, Ahlquist says.
"If the high degree of accuracy we saw in the pilot study holds in larger studies, this could be the first accurate, noninvasive approach to detecting precancerous polyps," Ahlquist says. "Large trials have shown that, while there is a reduction in deaths with the fecal blood screening test, it has very little impact on the incidence of colon cancer because it is not good at detecting these premalignant polyps."
Ahlquist says that certain technological problems have to be solved before the DNA test can be made widely available. The specimens currently are evaluated manually, but he says scientists are working on automating the process, which would allow the test to be widely read in labs across the country.
Robert Smith, PhD, director of cancer screening with the American Cancer Society, tells WebMD that the DNA screening test is "potentially a very important development." But he adds that a large percentage of undiagnosed colorectal cancers could be detected with available tests if more physicians would recommend them to their patients.
"Our big challenge right now is to get doctors to recommend the tests that we already have available," he says. "The fecal occult blood test is really a pretty good test, especially in combination with flexible sigmoidoscopy. And people tend to have these tests when their physicians recommend them, but doctors think their patients don't want them."