Activity of cabazitaxel in patients with metastatic castration-resistant prostate cancer after treatment with single or dual regimens of novel androgen receptor-targeting agents.

The purpose of this study was to evaluate the efficacy of cabazitaxel for patients with metastatic castration-resistant prostate cancer (mCRPC) after sequential therapy with docetaxel (DTX) and single or dual regimens of novel androgen receptor-axis-targeted (ARAT) agents. We retrospectively reviewed 84 consecutive patients treated with cabazitaxel at Kobe University Hospital and related hospitals from September 2014 to September 2016. The association of each prognostic parameter with progression-free survival (PFS) was evaluated, including the sequence of therapy. Patients were divided according to their treatment after receiving cabazitaxel as follows: group 1 (after DTX and single regimen of novel ARAT agent) and group 2 (after DTX and dual novel ARAT agents). Median PFS for cabazitaxel treatment was 10.3 months (range 4.5-14.2 months). Prostate-specific antigen (PSA) response rates (≥30%) were 46.8 and 46.1% in group 1 and group 2, respectively [p = 0.96, hazard ratio (HR) 1.02, 95% confidence interval (CI) 0.57-1.80]. PSA response rates (≥50%) were 43.8 and 26.9% in patients of group 1 and group 2, respectively (p = 0.18, HR 1.54, 95% CI 0.78-3.04). Univariate analysis revealed that PFS for cabazitaxel treatment was significantly associated with baseline alkaline phosphatase, bone metastasis, and prior sequential therapy. Multivariate analysis revealed that bone metastasis and prior sequential therapy were independently associated with PFS. Prior sequential therapy with single regimen or dual regimens of novel ARAT agents was independently associated with PFS of patients with mCRPC treated with cabazitaxel. The effect of cabazitaxel after the administration of DTX and single novel ARAT agent was more sustained.