New Colon Cancer Screening Test in the Works
Consumer-Friendly Test Under Study; DNA Findings Help Predict Risk
Oct. 28, 2010 -- A new, consumer-friendly test for colon cancer, once approved, could persuade more Americans to undergo screening for the deadly cancer, according to researchers presenting their findings on the test's effectiveness at a cancer conference in Philadelphia.
At the same meeting, other researchers reported that they have new clues about how DNA characteristics can help predict colon cancer risk.
The research was presented at the American Association for Cancer Research's special conference, Colorectal Cancer: Biology to Therapy.
Screening for Colon Cancer: Back Story
''One in every 17 of us will have colon cancer in our lifetime," says David Ahlquist, MD, professor of medicine and a consultant in gastroenterology at the Mayo Clinic in Rochester, Minn., who presented his findings on the new colon cancer screening test.
Although colon cancer is the second leading cause of cancer death for men and women in the U.S., many adults don't undergo the screenings once they reach age 50 (or earlier for those with a family history), Ahlquist told a news conference.
Estimates of how many adults undergo screening vary, but Ahlquist says probably only 40% adhere to the screening schedule over time.
One screening test, the colonoscopy, in which a flexible, lighted tube with a video camera is inserted to examine the colon, requires dietary restriction and preparation of the colon. Patients must often take time off work and need transportation home from the procedure.
Catching Colon Cancer: The New Test
The new test, a next-generation stool test known as a DNA methylation test, detects tumor-specific alterations or methylations in the DNA in the cells shed into the stool from cancerous or precancerous lesions. The test can be done at home without dietary restrictions or bowel preparation.
At the meeting, Ahlquist presented the results of the first clinical evaluation study, which enrolled 1,100 patients."We were pleased by the results of this first clinical study," he says.
The test found 64% of precancerous tumors that were bigger than a centimeter (less than a half inch) and found 85% of cancers.
Ahlquist called the 85% figure ''very high" and adds: "It would be very hard to find a noninvasive approach that could get that range."
The test also found tumors on both sides of the colon, Ahlquist says, a feat that is not always accomplished by colonoscopy. "These results were encouraging," he says.
The detection rate was 87% for cancers in stages I through III, considered the most curable, and 69% percent for stage IV, the most advanced.
The test is better at detecting cancer in early stages, he says, because the cells can become less methylated in later stages. The focus of the test is to catch cancers early, he says. "We are targeting early-stage cancers, and that's where the test does the best."
The median age of the patients was 60 (half were older, half younger).
Positive test results would be followed up with colonoscopy.
A clinical trial of the new stool test is expected to start in 2011, he says, and if all goes well the test could be available soon after that.
Ahlquist and Mayo Clinic are working in collaboration with Exact Sciences Corp. of Madison, Wis., to develop the test.