Fecal Blood Tests Effective at Spotting Colon Cancer
But they are underused, experts say
TUESDAY, Sept. 25, 2007 (HealthDay News) -- A new generation of fecal blood tests can screen for colon cancer with unprecedented accuracy, researchers report.
But the tests, although easily available, are greatly underused, said study author Dr. James Allison, an investigator with the Kaiser Permanente division of research in Oakland, Calif.
"A lot of gastroenterologists think that colonoscopy is the only test for colon cancer," Allison said.
But colonoscopy is also expensive, uncomfortable and carries the risk of damage such as internal bleeding, he said. A simple fecal occult blood test, costing less than $30 and done in minutes, can single out that small percentage of the general population that would benefit from colonoscopy, Allison said.
The study is published in the Sept. 25 issue of the Journal of the National Cancer Institute.
At least 10 fecal occult blood tests have been approved by the U.S. Food and Drug Administration, Allison said. The most widely used is Hemoccult, which has been shown in controlled trials to reduce mortality from colorectal cancer.
The two tests described in the new journal report use different methods to detect hidden blood. "Each one has different pluses and minuses," Allison said. "We need to find out which is best -- which we should be using in the United States and elsewhere."
One of the tests described in the journal report uses guaiac, the chemical in Hemoccult, as a detector. The other uses an immunochemical method. Screening of 5,841 people showed the immunochemical test to have a sensitivity of 81.8 percent, meaning that it detected that percentage of colorectal cancers and polyps. And it had a specificity -- the ability to determine which people did not have the conditions -- of 96.9 percent. The guaiac test was 64.3 percent sensitive and 90.1 percent specific.
Allison has been conducting something of a crusade to promote use of fecal occult blood tests to screen for colorectal cancer. "I am doing a tour of the United States and talking to primary-care physicians," he said.
Use of the tests not only saves lives but also reduces incidence of colorectal cancer by permitting removal of precancerous polyps, said Jack Mandel, chairman of the department of epidemiology at Emory University, who wrote an accompanying editorial in the journal.
"We did the first large study at the University of Minnesota in 1993 to show that fecal blood testing reduces mortality," Mandel said. "There were 50,000 people in that trial. Two years later, we showed that testing reduced the incidence of colorectal cancer."
Robert Smith, director of cancer screening for the American Cancer Society, said, "We recommend both guaiac-based tests and immunochemical tests. We recommend them for all adults age 50 and over."
No preference between the two methods is stated, because "at the time our last guidelines were updated, there was no clear advantage of one over another," Smith said.
"The challenge has been to get folks to use them, in particular to get doctors to adopt them in the office," he said.
To learn more about colorectal cancer screening, visit the U.S. National Cancer Institute.