A stool DNA test is a new approach for colon cancer screening. A stool DNA test is designed to identify recognizable DNA changes (DNA markers) in cells that are continually shed from the lining of the colon through stool. These markers are associated with the surfaces of the cells of precancerous polyps and cancerous tumors. Because the lining of the colon is always shedding cells, including cells from the surface of polyps and tumors, these markers are available in the stool. A stool DNA test can identify several of these markers, indicating the presence of precancerous polyps or colon cancer.

Because DNA changes may differ between colon cancers, stool DNA tests typically target multiple markers to achieve high detection rates. Also, because DNA markers may be present in only trace quantities in stool, very sensitive laboratory methods are required. Stool DNA testing has been shown to be more effective than fecal occult blood tests at detecting colon cancer and precancerous polyps. The new stool DNA tests demonstrate high detection rates of early-stage colon cancer. Unlike other noninvasive tests, the new stool DNA tests also can detect precancerous polyps.

One stool DNA test is currently available, but it has not been approved by the Food and Drug Administration (FDA). Next-generation stool DNA tests that have much improved detection rates are undergoing final clinical validation in a multicenter study by the FDA.

The method of screening for colon cancer using stool DNA testing has been endorsed by the American Cancer Society, the U.S. Multi-Society Task Force on Colorectal Cancer and the American College of Radiology, but not by the U.S. Preventive Services Task Force.

Jun. 18, 2011