Circulating DF3 and CA125 antigen levels in serum from patients with epithelial ovarian carcinoma.

The murine monoclonal antibody (MAb), designated DF3, reacts with a 300-kilodalton (kd) mammary epithelial antigen. A sequential double-determinant enzyme-linked immunoassay (EIA) has been developed to monitor circulating DF3 antigen. Previous studies have demonstrated that the use of the DF3 EIA provides a new and potentially useful marker to follow the clinical course of patients with metastatic breast cancer. In the present study, we have monitored circulating DF3 antigen in the serum of patients with epithelial ovarian carcinomas and non-ovarian gynecologic malignancies. Twenty-one of 45 patients (47%) with ovarian carcinoma had elevated DF3 antigen levels (greater than or equal to 30 U/mL). In contrast, three of 20 patients (15%) with non-ovarian gynecologic malignancies, and only four of 59 control women (7%) had elevation of circulating DF3 antigen. The difference between DF3 antigen values from patients with ovarian cancer and from controls was significant (P less than .001). The elevation of circulating DF3 antigen in ovarian cancer patients has also been confirmed by transblot assays. MAb DF3 reactivity occurred predominately with circulating antigens of molecular weights (mol wt) ranging from 300 to 450 kd. Furthermore, DF3 antigen levels have been shown to correlate with progression of disease in six patients with ovarian cancer and after resection of disease in two others. The half-life of circulating DF3 antigen was approximately 45 to 60 days. The results also demonstrate that DF3 antigen is distinct from CA125, a glycoprotein associated with coelomic epithelium and developmental amnion. The use of both the DF3 EIA and the immunoradiometric assay previously described to detect circulating CA125 suggests that determining levels of both markers may enhance the sensitivity of monitoring the course of ovarian cancer. Furthermore, the use of both assays may be useful in distinguishing ovarian cancer from other malignancies.