CA-549 is a high molecular weight, circulating marker for breast cancer defined by its reactivity to monoclonal antibody BC4E 549. CA-549 has recently been shown to be elevated in the sera of 50% of advanced breast cancer patients (n = 80), as compared to < 2.0% of benign breast disease patients (n = 79) or healthy individuals (n = 257). The purpose of this study was to evaluate CA-549 as a tool for monitoring the status of breast cancer disease. Serial serum specimens (n=381) from a total of 126 metastatic breast cancer patients were prospectively collected over 12 months and tested for CA-549 levels by immunoradiometric assay. The average percent increase in CA-549 levels in the 18 patients with disease progression was 115 f 103% (range = -27% to 440%), with 16 of 18 showing an increase of >25%. CA-549 levels decreased by a mean of -40.5 f 22.5% (range = 17% to -75%) in 12 patients with breast cancer regression, with 8 of 12 patients showing a decrease in serum CA-549 of >25%. For 18 patients diagnosed with clinically stable disease, the mean percent change in CA-549 was only 20.4 f 5.7%, range = (-27% to 24%), with 14 of 18 having changed by <25%. For patients with no evidence of disease, 75 of 78 were CA-549 negative throughout the study. Three of 78 patients showed borderline positive CA-549 elevation for at least one specimen. None of these 78 patients showed highly elevated This study confirms the highly specific nature of CA-549 as a breast cancer marker, and indicates that changes in CA- 549 levels are associated with the clinical course of the disease. Thus this test may be a useful tool to monitor response to treatment and recurrence of breast cancer.
CA-549.