The clinical validity of circulating tumor-associated antigens CEA and CA 19-9 in primary diagnosis and follow-up of patients with gastrointestinal malignancies.

The clinical validity of monitoring the tumor markers carcinoembryonic antigen (CEA) and CA 19-9 were investigated in 602 patients with colorectal, gastric, and pancreatic carcinomas. Sensitivity and specificity of the tests were evaluated preoperatively as well as in the postoperative follow-up for early detection of disease progression and recurrence. At a 95% level of specificity as calculated from a group of 150 patients with benign diseases, the CEA test with monoclonal antibody had a preoperative sensitivity of 39% in colorectal cancer and 21% in gastric cancer. On the other hand, CA 19-9 had a sensitivity of 19% in colorectal cancer, 21% in gastric cancer, and 89% in pancreatic cancer. In the postoperative follow-up it was found that a combination of both tumor marker tests was most profitable in gastric carcinomas, yielding an increase of sensitivity from 59%-94%, showing a high degree of complementarity. The gain in sensitivity provided by the CA 19-9 test over the CEA-test in colorectal cancer was very low. The gain in sensitivity, however, provided by the CEA test over the CA 19-9 test in pancreatic carcinoma was also very low. On the basis of these results it has to be recommended that cases with pancreatic carcinoma are to be monitored most efficiently with the CA 19-9 test, whereas in cases with colorectal cancer the CEA test should be used primarily. However, in gastric cancer the combined use of CEA and CA 19-9 represents a highly valuable basis for monitoring the course of disease.