Use of four monoclonal antibodies to detect tumor markers.

A combined panel of monoclonal antibodies to tumor markers was examined in the sera of 454 cancer patients to compare their reactivity. At least one of the four tumor-associated markers (CEA [caranoembryonic antigen], CA 19-9, CA 125, and SLEX [sialylated Lewisx epitope]) was positive with the sera of breast (43%), lung (64%), ovarian (54%), and colorectal (57%) cancer. Each tumor marker's reactivity was distinct in different patients, indicating that different epitopes were being detected. The number of tumor markers that were positive was associated with advancing stages of disease. In advanced stages with distant metastasis, 13% of the patients reacted with all four markers, whereas none of the early-stage patients did. In 14 cases of disease progression, the tumor markers increased with no instance of decrease. Among ten patients with regression, seven showed a decrease in tumor markers and three showed an increase. The authors conclude that the use of four tumor-associated markers expands the number of patients with a positive marker, thereby permitting the monitoring of some patients. Among 60 normals, one showed a weak reactivity with CEA and one with CA 125. Eventually, with more markers, it should be possible to monitor all patients.