BOSTON — A longtime study of more than 46,000 people has found that a simple but little-used screening test may help prevent people from getting colon cancer.
The test, known as fecal occult blood screening, looks for traces of blood in people's stool, a possible sign of a cancer or benign polyps that can be precursors to cancer. When these polyps are removed, cancer is prevented.
In the study, the colon cancer rate was reduced by as much as 20 percent among people who had the test.
The federally financed study, described in Thursday's issue of The New England Journal of Medicine, was conducted by Dr. Jack S. Mandel, a vice president of Exponent, a Menlo Park, Calif., research company, and his colleagues, most of whom are at the University of Minnesota.
Dr. Ernest Hawk, who is chief of the gastrointestinal cancer group at the National Cancer Institute's division of cancer prevention, said that it was already known the test reduced the colon cancer death rate, by allowing cancers to be detected in early stages.
But this was the first evidence that those who use the test can avoid colon cancer in the first place.
Hawk said that people whose colon cancer was detected in its earliest stage had a five-year survival rate of 90 percent while those whose cancer is discovered in the latest stage, stage D, had just an 8 percent survival rate.
"It's like the ultimate stage shift," Hawk said of the new results. "Not only do you not get stage D cancer, you don't get cancer at all."
Colon cancer kills 65,000 Americans a year, making it the leading cause of cancer deaths for men and women, after lung cancer.
Besides the fecal blood test, doctors detect it by performing colonoscopies, in which a flexible scope is used to examine the entire colon, and sigmoidoscopies, in which a scope is used to examine the lower part of the colon, where most cancers occur.
In addition, some doctors look for cancers with barium enemas.
But these tests are uncomfortable as well as being more expensive and elaborate than the fecal test. The fecal test is also the only one that has been shown in rigorous studies to reduce the colon cancer death rate, though doctors are convinced that the other tests have the same effect.
Few Americans have any colon cancer screening. The American Cancer Society estimates that only about a third of Americans older than 50 have ever been tested, and Mandel said it is estimated that at most a quarter of Americans older than 50 ever had a fecal occult blood test.
Mandel said that one reason for the dismal screening record is that doctors have tended not to recommend the test.
The fecal test, in particular, was mired in controversy because it was marketed for about 30 years before there was compelling evidence that it reduced the colon cancer death rate, he said.
During that time, "people had an opportunity to form an opinion," he noted, and many became skeptics.