The role of the CA 125 assay in the management of ovarian cancer.

The monoclonal antibody-based serum assay for CA 125 is a reliable indicator of tumor status in patients with ovarian cancer. This noninvasive technique also permits individualization of therapy as well as early detection of recurrence. CA 125 levels are elevated in over 80% of patients with epithelial ovarian cancers. While the level of CA 125 also is elevated in some patients with benign disease, nevertheless this assay can help differentiate benign from malignant pelvic masses, using 35 U/ml as a normal reference value. Rising, stable, or falling levels correlate with tumor progression, stability, or regression in over 90% of cases, though a rising CA 125 level may be a more reliable predictor than a falling level. Evaluation of serial CA 125 levels during initial chemotherapy is a good indicator of a patient's response to therapy as well as a good predictor of eventual outcome. Because of its high specificity, it is also hoped that the CA 125 assay will soon be used to screen for ovarian cancer.