Use of CA 125 monoclonal antibody to monitor patients with ovarian cancer

The monoclonal antibody (mAb) OC 125 reacts with an antigen on human ovarian carcinoma (OVCA) cells that is also shed into the body fluids and can be detected in patients' sera and/or ascites with a radioimmunometric assay. For the present study, serum CA 125 levels of patients (n = 36) with different stages of OVCA were investigated. Serum levels seem to correlate with tumor burden. In stages I and II (n = 12), 33% of patients were CA 125 positive, whereas 70% of stage III and IV patients (n = 24) were CA 125 positive. Mean serum levels were in 93 U/ml (stages I, II) and 279 U/ml (stages III, IV). CA 125 levels in ascites and in pleural effusions were manyfold higher than serum levels of the same patients (P less than 0.0001). Immunohistochemical investigations of CA 125 in different ovarian tumors (n = 91) revealed that 85% of malignant and 75% of borderline serous cystadenocarcinomas had detectable CA 125 surface expression. Furthermore, 71% of benign tumors showed the CA 125 epitope, whereas mucinous tumors were negative for this marker. One of six ovarian cancer cell lines was CA 125 positive, whereas in 6 of 11 patients, ascites-derived ovarian cancer cells (fresh and gradient isolated) were positive for this marker. The proportion of positive cells ranged from 10 to 90% in these samples. Intraperitoneal recombinant interferon-gamma (rIFN-gamma) therapy resulted in an increase in the number of cells reacting with CA 125. The results of monitoring in patients receiving different therapeutic regimens and/or agents demonstrate the usefulness of this marker.