Experimental Test for Colon Cancer Is Painless, Faster
Oct. 24, 2000 -- Thousands of colorectal cancer deaths could be prevented each year in the U.S. alone if people took advantage of early detection tests. But too many doctors fail to recommend them, and too many patients avoid taking advantage of them, primarily because the tests can range from merely uncomfortable to painful.
But now, if a new, noninvasive testing method proves effective in large multicenter studies, all of that might change. Researchers say if all goes well, the test, which measures specific DNA abnormalities unique to early stage cancer, could be clinically available in three years.
The method showed remarkable accuracy in the detection of patients with both colorectal cancers, and precancerous growths or polyps, in early testing conducted by researchers from Minnesota's Mayo Clinic. But study author David Ahlquist, MD, tells WebMD that its ease of use for the patient may be its greatest advantage over existing tests.
"We look at this test as being user-friendly and think it will contribute to overcoming barriers to the use of currently available tests," Ahlquist says. "We know that early detection through screening translates into saved lives. We also know that fewer than 30% of adults over 50 in this country have been screened, so there is a huge opportunity to improve on this."
Colorectal cancers are the second biggest cancer killer of people in the U.S. Because an estimated 56,000 Americans will die of the disease this year alone, and most of these deaths could be prevented if the cancer were diagnosed and treated early, it is widely recommended that people over the age of 50 undergo yearly fecal occult blood testing, which involves samples from three consecutive stools and can be done at home.
Flexible sigmoidoscopy, which involves the insertion of a flexible lighted tube and is done in a doctor's office, also is routinely recommended once every five years for this age group and for people with a family history of the disease.
More invasive and expensive procedures like colonoscopy or double contrast barium enema may be recommended if something suspicious is found with the first two procedures.
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.