New colon cancer screening test

Sep 26 2007

A new version of a colon cancer screening test effectively detects colorectal cancer and may be a good replacement for the test that is currently used, according to a study in the September 25 Journal of the National Cancer Institute.

Fecal occult blood testing, which looks for hidden blood in the stool, is one of the recommended options for colorectal cancer screening. One widely used test—the unrehydrated guaiac test—is recommended by the U.S. Preventive Services Task Force and the Institute of Medicine because it has been shown to decrease colorectal cancer mortality in randomized clinical trials. Nonetheless, it does not detect all colorectal cancers. Employing newer tests may improve colon cancer detection.

James Allison, M.D., of Kaiser Permanente's division of research in Oakland, Calif., and colleagues compared the performance of two newer fecal occult blood tests—a more sensitive guaiac test and a fecal immunochemical test—in 5,841 people with an average risk of colorectal cancer. They looked at the tests' ability to detect colorectal cancers and polyps in people with the disease (sensitivity) and their ability to determine which people do not have the disease (specificity).

The fecal immunochemical test had a sensitivity of 81.8% for detecting colorectal cancers and a specificity of 96.9%. The guaiac test was 64.3% sensitive for detecting colorectal cancers and 90.1% specific.

“The suggestion that [fecal occult blood testing] has a useful role in colon cancer screening is further strengthened by data suggesting that newer [fecal occult blood tests] are substantially more sensitive than the older ones on which past recommendations were based,” the authors write.

In an accompanying editorial, Jack Mandel, Ph.D., of Emory University in Atlanta discusses the evidence in favor of immunochemical tests over guaiac tests. “Which immunochemical test is best is yet to be determined, but evidence is rapidly mounting that immunochemical is superior to guaiac,” he writes.