Estramustine Phosphate Monotherapy in Castration-Resistant Prostate Cancer Patients Who Cannot Receive Cytotoxic Chemotherapy

Abstract

Purpose To investigate whether estramustine phosphate (EMP) monotherapy is applicable to castration-resistant prostate cancer (CRPC) patients who cannot receive cytotoxic chemotherapy. Materials and Methods This retrospective single-arm study was conducted in CRPC patients who had not experienced cytotoxic chemotherapy and received EMP monotherapy (560 mg/day) at 2 institutions from 2008 to 2017. We analyzed prostate-specific antigen (PSA) responses, overall survival, and adverse effects of EMP treatment. Results A total of 28 patients were analyzed. A reduction in serum PSA was observed in 11 patients (39.3%). Seven cases (25.9%) achieved more than 25% reduction of PSA, and 5 of them (18.5%) experienced more than 50% reduction. Median overall survival was 23 months (interquartile range, 10–60 months). Multivariable analyses demonstrated that low level of PSA at diagnosis of CRPC and long duration of prior androgen deprivation therapy were independent favorable factors predicting long-term overall survival. Adverse effects were edema (n=2; grade 2), nausea/vomiting (n=1; grade 2), gynecomastia (n=1; grade 2), and dyspnea (n=1; grade 1). Neither throm-boembolic event nor grade 3–5 toxicity was observed. There was no discontinuation caused by side effects of EMP. Conclusions EMP monotherapy could be considered as a safe treatment option with some effectiveness for CRPC patients who did not undergo cytotoxic chemotherapy. EMP is not generally recommended anticancer drug in the current guidelines for CRPC, but EMP monotherapy is thought to have an alternative role when a standard treat-ment cannot be selected due to patient's age, health condition, or comorbidity. Key Words: Castration-resistant prostatic neoplasm; Estramustine.