Phase II study of carboplatin and etoposide in patients with anaplastic progressive metastatic castration-resistant prostate cancer (mCRPC) with or without neuroendocrine differentiation: results of the French Genito-Urinary Tumor Group (GETUG) P01 trial

Background: In the evolution of metastatic castration-resistant prostate cancer (mCRPC), patients present visceral metastases with or without neuroendocrine differentiation in 20% of cases. Patients and methods: We assessed the efficacy and toxicity of a platinum-based chemotherapy regimen in mCRPC patients with either neuroendocrine differentiation defined by high serum levels of chromogranin A (CgA) and neuron-specific enolase (NSE) or visceral metastases. Patients received the combination of carboplatin and etoposide every 3 weeks. Efficacy end points included prostate-specific antigen (PSA) and neuroendocrine marker response, objective response and toxicity. Results: Of the 60 patients included from April 2005 to January 2008, 78.6% had bone metastases, 46.4% had lymph node involvement and 57.1% had liver and/or lung localizations. The objective response rate was 8.9% in the 46 patients with measurable disease. A neuroendocrine response was observed in 31% of cases for NSE and 7% for CgA. The PSA response rate was 8%. The most common grade 3-4 treatment-related toxic effects were neutropenia (65.5%), thrombocytopenia (32.7%) and anemia (27.3%). There was 7.2% febrile neutropenia, with one toxicity-related death. The median follow-up was 9.3 months [95% confidence interval (CI) 0.2-27.1] and the median overall survival 9.6 months (95% CI 8.7-12.7). Conclusion: The benefit-risk ratio of this regimen seems unfavorable due to poor response and high toxicity.