FDA backs non-invasive, stool-based DNA colon cancer test

A U.S. Food and Drug Administration (FDA) advisory panel unanimously voted in favor of a new non-invasive, stool-based DNA colon cancer test Thursday.

The alternative screening method, called Cologuard, detected 92.3 percent of colorectal cancers in patients based on a combination of DNA and hemoglobin markers in a clinical trial. It was also found to be 94 percent effective in detecting early stage cancers.

The FDA's committee approved the Exact Sciences' test in a 10-0 vote, stating that its benefits outweighed the risks.

"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."

If the FDA follows the panel's advice, which it often does, and approves Cologuard, patients who test positive for colon cancer using the test would then undergo a colonoscopy. The test analyzes abnormal DNA found in the stool, a less-invasive method than a traditional colonoscopy. A colonoscopy is still the most accurate way of detecting polyps in the colon, however, and involves inserting a flexible tube into the colon.

Colorectal cancer is the second leading cause of cancer-related deaths in the United States, though it is considered one of the most preventable. Only one in three adults over age 50 actually get the recommended annual colon cancer screenings, according to estimates.

"We know that colorectal cancer can be prevented and can be highly treatable if found early through screening" said lead author Dr. Thomas F. Imperiale of the Indiana University School of Medicine.

However, Cologuard also returned more false positives, CBS News chief medical correspondent Dr. Jon LaPook pointed out.

"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 to CBS. "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."