Prior Estrogen Therapy as a Predictor of Response to Subsequent Estramustine-Based Chemotherapy in Patients with Androgen-Independent Prostate Cancer

Abstract

BackgroundHormone-refractory prostate cancer (HRPC) has modest response rates to second-line estrogenic agents such as diethylstilbestrol and the herbal product PC SPES. Estramustine phosphate (EMP) is a microtubule inhibitory agent with estrogenic properties commonly used in patients with metastatic HRPC. To determine whether previous response to second-line estrogen therapy would predict subsequent response to EMP-based chemotherapy, a retrospective study was conducted. Patients and MethodsPatients with HRPC previously treated with second-line estrogenic therapy who subsequently received EMPbased chemotherapy were enrolled in a retrospective analysis. The progression of disease or response to treatment was determined with use of standard prostate-specific antigen (PSA) criteria and Response Evaluation Criteria in Solid Tumors. ResultsSeventy-eight patients were included in the analysis. Twenty-five patients with disease progression after receiving estrogen therapy received subsequent EMP-based chemotherapy. Overall, initial PSA response to any estrogen therapy was 54%. The overall PSA response to EMP-based chemotherapy was 60%, and the objective response was 36%. The PSA response to subsequent EMP-based chemotherapy was independent of patients having a previous response to estrogen therapy (70% vs. 53%; P = 0.68). The median overall survival for patients receiving estrogenic therapy and subsequent EMPbased chemotherapy was 12.7 months. ConclusionPrevious response to second-line hormonal maneuvers with estrogen therapy does not predict subsequent response to EMP-based chemotherapy.