Jonathan M. Niloff

The murine monoclonal antibody OC 125 reacts with an antigen (CA 125) common to most nonmucinous epithelial ovarian carcinomas. An assay has been developed to detect CA 125 in serum. By this assay, only 1 per cent of 888 apparently healthy persons and 6 per cent of 143 patients with nonmalignant disease had serum CA 125 levels above 35 U per milliliter. In contrast, 83 of 101 patients (82 per cent) with surgically demonstrated ovarian carcinoma had elevated levels of antigen. In 38 patients with epithelial ovarian carcinoma monitored on 2 to 18 occasions during 2 to 60 months, antigen levels ranged from less than 1 to more than 8000 U per milliliter. Rising or falling levels of CA 125 correlated with progression or regression of disease in 42 of 45 instances (93 per cent). Determination of CA 125 levels may aid in monitoring the response to treatment in patients with epithelial ovarian cancer.

Invasive cervical cancer is uncommon in the United States, with an incidence of 15,800 cases and 4800 deaths in 1995.1 This relatively low incidence is largely due to the effectiveness of screening programs that assess cervical cytology by Pap smear. On a global scale, however, cancer of the cervix is a major cause of death, especially in Third World countries, where such screening is often not routinely performed. Pap-smear screening is designed to detect precursor lesions in cervical epithelium, which may antedate the development of invasive cancer by several years. In contrast to other screening strategies, such as mammography, which . . .

CA 125 is an antigenic determinant expressed by greater than 80% of nonmucinous epithelial ovarian carcinomas. An immunoradiometric assay has been developed using a murine monoclonal antibody (OC125) to quantitate CA 125 in human serum. This immunoradiometric assay was optimized for specificity, sensitivity, and performance characteristics. Using a simultaneous immunoradiometric assay, the mean CA 125 concentration in 56 sera from healthy individuals was 11.2 +/- 5.4 (S.D.) units/ml, with 9.7 +/- 3.2 units/ml for 30 males and 13.1 +/- 6.8 units/ml for 26 females. A reference value of 35 units/ml included all 56 normals and excluded 86 of 105 (82%) ovarian carcinoma patients. This reference value also excluded 9 of 142 patients (6%) with benign diseases, but if the upper limit of normal was set at 65 units/ml, only 3 of 142 (2%) patients with benign diseases had elevated serum CA 125 levels, whereas 77 of 105 (73%) ovarian carcinoma patient sera remained positive. The ability of researchers, with this assay, to discriminate between CA 125 values in sera of patients with ovarian carcinoma and those of healthy individuals and patients with benign disease suggests that the assay deserves continued evaluation for monitoring and early diagnosis of ovarian cancer.