929P - Low-Dose Dethylstilbestrol in Castration-Resistant Prostate Cancer

Abstract

ABSTRACT Introduction The role of sequential lines of hormone therapy in castration-resistant prostate cancer (CRPC) remains unclear. Currently, the standard treatment for patients with CRPC is chemotherapy. Diethylstilbestrol (DES) is a synthetic estrogen with anti-tumour properties, which could be effective in these patients, before chemotherapy. OBJECTIVE: To determine the efficacy and safety of low-dose DES in second-line hormonal therapy for CRPC patients in a single institution. Methods Between 2007 and 2012, a total of 31 patients with metastatic CRPC received DES 1 mg daily. All patients had progression after central androgenic suppression and at least one line of androgen antagonists (bicalutamide and/or flutamide). Central androgenic supression with bilateral orchiectomy or a gonadotropin-releasing hormone agonist was maintained. Aspirin 100 mg daily was administered to all patients to minimize risk of thromboembolism. The data of PSA response (defined as a 50% reduction), progression-free survival (PFS), overall survival and adverse events were collected and analyzed. Results The median age was 76,8 years. The PSA response rate was 55%. After a median follow up of 22 months, the median PFS was 12 months. Only one patient died at the time. The main adverse event was gynecomastia (11/31, 35.4%) and no thrombotic event was recorded. Conclusion Low-dose DES appears to be safe and effective for metastatic CRPC before initiating chemotherapy. Disclosure All authors have declared no conflicts of interest.