Colonoscopy alternative, but not yet a replacement

Andrew Pollack / New York Times News Service /


Published Apr 19, 2013 at 05:00AM / Updated Nov 19, 2013 at 12:31AM

A new noninvasive screening test can detect most cases of colorectal cancer and also many precancerous polyps, potentially helping to sharply reduce the death toll from the disease, according to results of a study released Thursday.

Still, the results fell short of expectations, even those of the company that developed the test, the Exact Sciences Corp., which said its test detected 92 percent of the cancers picked up by colonoscopy, and 42 percent of potentially precancerous polyps. It had a false positive rate of 13 percent.

The test looks for alterations in human DNA found in a stool sample. The company contends that people will not find it off-putting to deposit a sample of their stool in the company’s collection apparatus and mail it to a laboratory.

The new test, called Cologuard, would not replace a colonoscopy, which remains the gold standard for colorectal screening, in part because any polyps detected can also be removed during a colonoscopy, possibly preventing cancer.

But about half of people older than 50, the recommended age to start screening for colorectal cancer, are either not adequately screened or not screened at all, in part because colonoscopy is invasive, uncomfortable, expensive and time-consuming.

Exact Sciences says the noninvasive test could allow more people to be screened, and those with a positive result could then get a colonoscopy.

Exact Sciences, which is based in Madison, Wis., said it would soon complete its application to the Food and Drug Administration seeking approval of the Cologuard test.

There were about 143,000 new cases of colorectal cancer and 52,000 deaths in the United States last year, making it the second-leading cause of cancer death behind lung cancer, according to the American Cancer Society.

Dr. Deborah Fisher, an associate professor of medicine at Duke University, who was not involved in the study, said the Cologuard test appeared to be a viable option, but only one of several. “I don’t think this is the holy grail,” said Fisher, a gastroenterologist who is a consultant to Epigenomics, a company developing a test that could compete with Cologuard.

Fisher said existing noninvasive tests that look for blood in the stool can detect around 80 percent of cancers and 20 to 40 percent of polyps. These tests cost about $25, she said, while the Cologuard test is expected to cost a few hundred dollars.