FDA Panel Backs Non-Invasive Alternative For Colon Cancer Screening

By: CBS/AP
By: CBS/AP

(CBS/AP) - A panel of Food and Drug Administration (FDA) advisers has voted to endorse an experimental stool test that uses DNA to detect colon cancer and precancerous growths.

The FDA's committee of genetic experts voted 10-0 that the benefits of Exact Sciences' Cologuard test outweigh its risks. The vote amounts to a recommendation for the FDA to approve the test from Exact Sciences of Madison, Wis. The agency is not required to follow the panel's advice, but often does.

"We are pleased the committee strongly supported Cologuard's approval," Kevin T. Conroy, chairman and chief executive of Exact Sciences, said in a statement. "We look forward to continuing our work with the FDA to complete its review of Cologuard and remain committed to addressing the growing unmet needs in colorectal cancer screening."

Doctors have long used stool tests to look for hidden blood, a sign of possible tumors and precancerous polyps.

Cologuard was 92-percent effective for spotting colon cancer, and 94 percent effective at detecting early-stage cancers (I, II) when they're most curable.

The Cologuard tests the stool for altered DNA that gets shed during digestion. That appears to make it a more effective option than the FIT test (which tends to be 74 percent effective at catching cancers).

Not all cancers bleed to the point that an FIT can pick them up. The same goes for polyps that are large enough and might turn into cancer.

Cologuard and other DNA tests in development detect minute genetic changes associated with cancer cells in the colon.

On Wednesday, the same FDA panel of experts voted 5-4, with one abstention, that the benefits of the Epi proColon kit from Epigenomics outweigh the risks. That tests blood samples, not stool.

Approving such new tests could reshuffle current practice. The FDA staff's review of Cologuard, released earlier this week, suggests Cologuard would require additional follow-up studies to see how accurately it performs over several years.

Current federal guidelines recommend traditional blood stool samples every year for patients between ages 50 and 75, but only about 60 percent do so.

It's unclear how often Cologuard would need to be used. It's expected to cost significantly more than blood stool tests, which run about $25.

However, Cologuard also returned more false positives, CBS News chief medical correspondent Dr. Jon LaPook pointed out last week, reporting growths when none were present.

"I can tell you as a gastroenterologist that's going to be a big problem, because if the test says there's a colon cancer, it doesn't tell me where in the colon it is," he explained at the time. "I'm winding up the colon, I'm looking for this cancer, it's not there, and that's going to be highly stressful. So clearly they're going to have perfect this test a little bit more," he said.

Colorectal cancer is the second-leading cause of U.S. cancer deaths, with over 50,000 expected this year, according to the American Cancer Society. Deaths from the disease have been declining for more than two decades as screenings have increased.

Colonoscopy remains the most accurate test, but many adults are reluctant to undergo the invasive procedure.

© 2014 CBS Interactive Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.


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