PREDICTIVE VALUE OF SERUM MEDROXYPROGESTERONE ACETATE CONCENTRATION FOR RESPONSE IN ADVANCED OR RECURRENT BREAST-CANCER

Medroxyprogesterone acetate ((MPA) is one of the most commonly prescri bed drugs for endocrine therapy of metastatic breast cancer. In this s tudy, the serum MPA concentration was measured by high-performance liq uid chromatography (HPLC) and evaluated for its usefulness in predicti ng the response in 79 cases of advanced or recurrent breast cancers. O verall, 29 patients (37%) achieved an objective response. The response rate correlated significantly with the oestrogen receptor (ER) status (P= 0.03), proliferative activity determined by DNA polymerase alpha (P= 0.04), the disease-free interval (DFI) (P= 0.05) and the serum MPA concentration (P< 0.001). Patients with PR-positive tumours, lower pr oliferative activity, a longer (DFI) or a higher serum MPA concentrati on responded more frequently. The mean serum MPA concentration in the responders with ER-positive tumours (P= 0.01) or tumours with a lower proliferative activity (P= 0.008) were significantly lower than in cas es with PR-negative tumours or tumours with a higher proliferative act ivity, respectively. Cases with soft tissue metastases showed response s at significantly lower MPA concentrations (P = 0.003) than those wit h bone or visceral metastases. Furthermore, there was a dramatic decre ase in the MPA concentration when a responder with a high concentratio n became unresponsive to the therapy. Thus, the serum MPA concentratio n is a determining factor for the response to treatment. (C) 1997 Else vier Science Ltd.