Combining carboplatin and etoposide in docetaxel-pretreated patients with castration-resistant prostate cancer: a prospective study evaluating also neuroendocrine features

Background: There is currently no standard treatment for patients with castration-resistant prostate cancer (CRPC) whose disease progresses after docetaxel-based chemotherapy. The purpose of this study was to prospectively assess the anticancer activity and tolerance of the carboplatin-etoposide combination in this setting while evaluating neuroendocrine (NE) features. Patients and methods: Patients with CRPC and metastases who experienced failure after first-line docetaxel-based chemotherapy were treated with carboplatin (area under the curve 5, day 1) and etoposide (80 mg/m(2)/day from days 1 to 3), repeated every 3 weeks. The association between serum chromogranin A (CgA), neuron-specific enolase (NSE), prostate-specific antigen-doubling time (PSADT), and treatment efficacy was studied. Results: Forty patients with CRPC who had received docetaxel with (n = 20) or without (n = 20) estramustine received the carboplatin-etoposide combination as second-line chemotherapy. A prostate-specific antigen (PSA) response defined as a PSA decline >= 50% was achieved in nine patients (23%). Median progression-free survival (PFS) was 2.1 months (range 0.6-9.6) and median overall survival was 19 months (range 2.1-27.7). Pain response was achieved in 15 (53%) of 28 assessable patients. Toxicity, including mainly grades 3-4 anaemia (25%) and febrile neutropenia in only 2% of patients, was manageable. Baseline CgA, NSE, or PSADT were not significant predictors for response or PFS. The PSA response rates were 18% and 31% in patients with normal and elevated serum CgA, respectively. It was 25% and 20%, respectively, in patients with normal and elevated serum NSE. Conclusions: Combining carboplatin and etoposide as second-line chemotherapy in patients with CRPC is active and well tolerated in spite of a limited PFS. Activity was observed in CRPC with and without NE features.