TA90-IC, a new marker for advanced colon cancer

Background: Although carcinoembryonic antigen (CEA) is the most frequently used marker for colon cancer, it is elevated in only 70% of patients with a dvanced disease and in even fewer patients with earlier stages of disease. We previously identified a 90-kDa glycoprotein, TA90, which is present in s erum in the form of circulating immune complexes. TA90 is found in a variet y of solid neoplasms but rarely in healthy controls (3.2%). We hypothesized that this new tumor-associated antigen may be a useful marker for colon ca ncer. Methods: Serum samples from 59 patients with known colon adenocarcinoma wer e analyzed for the presence of CEA and TA90. Fifty-one (86%) patients had d istant metastases; the remaining patients had clinically localized primary colon cancer. A murine monoclonal antibody-based enzyme-linked immunosorben t assay was used to measure concentrations of TA90-specific circulating imm une complexes (TA90-IC). A positive value was defined as an optical density of more than 0.410 at 405 nm. Forty-seven (80%) of the 59 patients had ser um samples for TA90 and CEA drawn at the same time. Results: TA90-IC concentrations were elevated more frequently than CEA conc entrations (82.9% vs. 70.2%; P = .134). The combination of both markers ide ntified more patients with colon carcinoma than did either marker alone (93 .6%; P < .001). Conclusions: Concomitant use of TA90-IC and CEA identified 93.6% of patient s with advanced colon cancer. The role of TA90-IC in screening and monitori ng progression of earlier disease deserves further investigation.