Test for RNA in stool may spot colon cancer

The presence of RNA for the enzyme cyclooxygenase 2 (COX-2) in feces probably indicates the presence of colorectal cancer, according to results of a pilot study conducted in Japan.

High levels of COX-2 are found in upwards of 80 percent of colon cancers, Dr. Shigeru Kanaoka and colleagues from Hamamatsu University School of Medicine note in an article in the medical journal Gastroenterology.

Kanaoka told AMN Health that "our results strongly suggest that the fecal COX-2 assay is a strong candidate" test for colorectal cancer screening.

To evaluate the accuracy of the assay, the researchers studied 29 patients with colorectal cancer and a comparison group of 22 healthy people. The team measured levels of RNA in stool for both COX-2 and another cancer marker, carcinoembryonic antigen (CEA).

The fecal COX-2 assay detected 90 percent of cancers, with no false-positive results. The accuracy did not depend on how advanced the tumor was, its location in the colon, or its size.

The fecal CEA assay detected 100 percent of bowel cancers, but it also gave false-positive results 95 percent of the time - making it less useful for screening purposes.

With further refinement and confirmatory studies, the investigators conclude that the fecal COX-2 assay "would be attractive for colorectal cancer screening." Kanaoka added that his team will now "add other molecules to this assay to further improve sensitivity."

SOURCE: Gastroenterology, August 2004.