Carbohydrate Antigen 19-5 (CA19-5)

Carcinoembryonic antigen (CEA) is a well-described human tumor-associated antigen most useful clinically in colon cancer. However, the clinical usefulness of CEA is limited by the marker's overall poor specificity and low sensitivity in patients with minimal disease. CA 195 is a recently discovered human tumor-associated glycoprotein that can be measured in serum using an immunoradiometric assay. CA 195 is expressed on the membrane of human colon cancer cells and shares an epitope with the Lewis A blood group antigens. The authors initiated a study to compare the clinical utility of serum CA 195 with CEA in patients with advanced cancer.CA 195 is not superior to CEA as an indicator of disease activity in advanced colon cancer or other solid tumors. However, studies utilizing CA 195 in the detection of early relapses of colon cancer may be warranted.