Efficacy of estramustine phosphate according to risk classification of castration-resistant prostate cancer

Treatment options for patients who progressed to castration-resistant prostate cancer (CRPC) are very limited. The purpose of this study was to assess the efficacy of estramustine phosphate (EMP) in patients with CRPC, grouped according to the risk classification advocated by Armstrong et al. and to identify candidates for EMP treatment. Between March 2003 and July 2010, 82 patients with CRPC were treated with 280 or 560 mg EMP per os daily until disease progression or occurrence of unacceptable adverse events. Prostate-specific antigen (PSA) response and overall survival were evaluated according to risk classification. 52 (67%) patients achieved PSA decline. Rates of PSA decline in the good-, intermediate-, and poor-risk groups were 77, 71, and 25%, respectively, significantly higher in the good- and intermediate-risk groups than the poor-risk group (p = 0.03). The median overall survival times in good-, intermediate-, and poor-risk groups were 21, 19, and 9 months, respectively (p = 0.005 for good vs intermediate, p = 0.001 for intermediate vs poor). When the intermediate-risk group was divided into two subgroups by PSA doubling time (PSADT), men with PSADT ≥ 2 months achieved higher PSA response rate (88%) and longer survival (22 months) than those with PSADT < 2 months (53%, 15 months). Patients with good-risk or intermediate-risk with PSA doubling time ≥2 months achieved favourable PSA response and survival and may benefit from chemotherapy with EMP.