[Monoclonal antibodies in the diagnosis and follow-up of ovarian cancer. CA 125 as a tumor marker. A cooperative study of the Gynecologic Tumor Marker Group (GTMG)].

The clinical validity of using the cancer antigen (CA) 125--a surface antigen on malignant epithelial ovarian tumors--for diagnosis and follow-up of ovarian cancer was investigated in a cooperative study. Using a monoclonal antibody (OC 125) to detect CA 125, the sera of 850 patients were analyzed by immunoradiometric assay (IRMA-Kit Centocor). For 199 patients with ovarian cancer, a preoperative sensitivity of 83% and 74% resulted for the usual cut-off points (greater than or equal to 35 and greater than or equal to 65 U/ml respectively). The positivity rates and quantiles correlated with the stage of disease (FIGO) and with the tumor debulking achieved at primary surgery. The most frequent histological types (serous cyst-adenoma and the undifferentiated carcinoma of the ovary) showed the highest positivity rates (80% and 90%, respectively, for cut-off at greater than or equal to 65 U/ml). Elevated CA 125 values were found in 74% of the cases with a relapse and in 79% of the patients with advanced disease (cut-off, greater than or equal to 65 U/ml) in the follow-up of ovarian cancer. We recommend cut-off at greater than or equal to 65 U/ml, because the values for only 1% of the female healthy controls (n = 251) were above this level. Also 17% of the patients with adnexitis and 8% with benign neoplasias of the ovary showed elevated titers. Therefore CA 125 should not be used for mass screening of ovarian carcinoma. However, it is a helpful laboratory tool in the diagnosis of recurrence and the surveillance of patients with ovarian cancer.