Fecal COX-2 mRNA assay may spot colorectal cancer

The presence of cyclooxygenase 2 (COX-2) mRNA in feces may be indicative of colorectal cancer (CRC), irrespective of clinical stage, according to results of a pilot study conducted in Japan and reported in the August issue of Gastroenterology.

COX-2 is overexpressed in upwards of 80% of CRCs, Dr. Shigeru Kanaoka and colleagues from Hamamatsu University School of Medicine observe. He told Reuters Health that “our results strongly suggest that the fecal COX-2 assay is a strong candidate” test for CRC screening. To evaluate the discriminatory power of the assay, the researchers studied 29 patients with CRC and 22 healthy controls. The team used nested reverse-transcription polymerase chain reaction to determine expression levels of both COX-2 and carcinoembryonic antigen (CEA). The fecal COX-2 assay was highly sensitive (90%) and specific (100%) in detection of CRC, and there was no significant difference between levels of COX-2 mRNA and Dukes’ stage, location, or size of tumors. The team observed COX-2 mRNA in 3 of 4 Dukes’ stage A tumors, 13 of 14 Dukes’ stage B tumors, and 10 of 11 Dukes’ stage C or D tumors, as well as in 5 of 7 patients with proximal cancer and 21 of 22 with distal cancer. The fecal CEA assay had a sensitivity of 100% but a specificity of only 5% in the detection of CRC. With further refinement and confirmatory studies, the investigators conclude that the fecal COX-2 assay “would be attractive for CRC screening.” Dr. Kanaoka added that the team will now “add other molecules to this assay to further improve sensitivity.” (Source: Gastroenterology 2004;127:422-427: Reuters Health News: Oncolink: September 2004.)