Activity of gemcitabine-oxalipaltin (GemOx) plus prednisolone in patients with castration-resistant prostate cancer (CRPC) for whom docetaxel-based chemotherapy failed.

Abstract

108 Background: We assessed the cytotoxic effects of the gemcitabine in combination with oxaliplatin (GemOx) in prostate cancer cell lines and evaluated the efficacy and safety of GemOx in patients with metastatic castration-resistant prostate cancer (CRPC) who failed docetaxel based chemotherapy. Methods: Gemcitabine and oxaliplatin were preclinically tested for their cytotoxic activity in LNCaP, PC3 and DU145 cell lines. The combined drug effects were evaluated using the Chou and Taladay analysis. Clinically, patients with CRPC who failed prior docetaxel chemotherapy were treated with gemcitabine 1,000 mg/m2 at fixed-dose rate (10 mg/m2/min) and oxaliplatin 100 mg/m2 intravenously every 2 weeks and prednisolone 5 mg orally twice daily. Unless disease progression or intolerability develops, treatment could be continued until 12 cycles. Primary endpoint was PSA response rate (PCWG 1.0 criteria). Results: The IC50of gemcitabine and oxaliplatin were, respectively, 1.25 μM and 0.69 μM for LNCaP cells; 50.00+ μM and 12.81 μM for PC3 cells; and 11.23 μM and 11.04 μM for DU145 cells. The GemOx combination displayed synergistic effects in all 3 cell lines. In phase II study, 31 patients were accrued. At the time of this analysis 7 patients were still continuing treatment. The median age was 67 years (range 57 ~ 81) and the median dose of docetaxel exposure was 525 mg/m2. A total of 231 cycles administered with a median of 9 cycles per patient. PSA responses were observed in 52% (95% CI, 34~69) and partial responses were observed in 7 of 10 patients with measurable disease. Out of 23 patients, 10 patients achieved pain response (44%). With a median FU duration of 8.0 months, the median time to PSA progression was 6.4 months (95% CI, 3.5~9.2). Peripheral neuropathy developed in 78% of patients but remained of grade 1 ~2 intensities. Frequently observed grade 3 or 4 toxicities were neutropenia (10%), thrombocytopenia (10%), anemia (3%), and diarrhea (3%). Conclusions: GemOx is active and well tolerated in patients with CPRC after docetaxel failure and deserves further investigation in this setting (NCT 01487720). Clinical trial information: NCT01487720.