The prognostic importance of tumor markers in adenocarcinomas of the gastrointestinal tract.

Although no serological tumor marker has yet been shown to be sufficiently sensitive and specific to be used in screening for colorectal, gastric, or pancreatic cancers, elevated pre-operative levels of carcinoembryonic antigen and carbohydrate antigen (CA) 19-9 correlate with advances stages of disease and a poorer clinical outcome. Monitoring of serum carcinoembryonic antigen after primary resection of colorectal cancer may identify a small percentage of asymptomatic patients with recurrent disease who are amenable to a second surgical procedure with curative intent. A new class of tumor markers that recognize cytokeratins, which comprise the intermediate filaments of the cytoskeletons of epithelial cells, is being evaluated as a prognostic factor in colorectal and gastric cancer. Elevated mRNA expression of matrix metalloproteinases and their inhibitors in tumor tissue compared with normal intestinal mucosa predicts for a poor prognosis after primary management of colorectal cancer. CA 19-9, CA 72-4, and CYFRA 21-1 may convey prognostic information in gastric cancer. CA 19-9 appears to be the best overall tumor marker for pancreatic cancer, and a subsequent rise after postoperative normalization may precede clinical detection of recurrent disease. CAM 17.1 is a new marker that has similar sensitivity but better specificity than CA 19-9 in pancreatic cancer. The utility of serial monitoring of these tumor markers in patients with advanced disease is less well established but may become helpful if more effective systemic therapy is developed.