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New Stool Test Better at Detecting Cancer

A new test that checks stool for signs of colon cancer caught 90 percent of cases -- far better than current stool tests, experts report.

A new test that checks stool for signs of colon cancer caught 90 percent of cases — far better than current stool tests, researchers reported Tuesday. But it’s still no substitute for a colonoscopy, experts cautioned.

The test, called Cologuard, is up for approval by the Food and Drug Administration later this month. It might provide a more accurate alternative for people who simply refuse to get colonoscopies, doctors agreed.

“For those patients unwilling or unable to have a colonoscopy, this offers an excellent choice, one we haven’t had to now,” said Dr. Felice Schnoll-Sussman, a gastroenterologist at New York Presbyterian Weill-Cornell Medical Center, who was not involved in the research.

The test isn’t very good at finding little growths that have not yet become cancerous, researchers report in the New England Journal of Medicine. That’s why colonoscopy remains the gold standard — doctors can find and remove those growths before they ever become dangerous.

Colon cancer is the second leading cause of cancer death in the United States, after lung cancer. It kills 50,000 people a year and is diagnosed in more than 136,000, according to the American Cancer Society. But the American Cancer Society reported earlier this week that the rates of colon cancer had dropped 30 percent over the past 10 years in people over 50, mostly due to screening.

Experts recommend that everyone over 50 get a colonoscopy, and new laws mean insurance companies have to pay for them.

“We want to find those patients when the cancer is still localized and amenable by surgery,” said Dr. Andrew Chan, a gastroenterologist at Massachusetts General Hospital.

Yet only 45 percent of Americans aged 50 to 64 have had one. Some are reluctant because the procedure requires a good clean-out with a laxative, sedation and a device inserted up through the rectum. A stool test can be done at home.

Dr. Thomas Imperiale of Indiana University, Dr. David Ransohoff of the University of North Carolina and colleagues tested 10,000 volunteers with the new test, which looks for damaged DNA from colon tumors. All the volunteers were scheduled to get colonoscopies, and they took both the old and the new stool tests, too.

Colonoscopy showed that 65 had colorectal cancer. The old stool test spotted 48 of these tumors, while the new test spotted 60 of them. And colonoscopy detected pre-cancerous growths in 822 of the people; the new DNA test spotted 322 or about 42 percent of these while the old stool test found 180 of them, or about 24 percent.

“A test like this can’t replace colonoscopy. The best it can do is to delay it, perhaps for a long time,” Imperiale told NBC News.