Prognostic significance of grade 3/4 neutropenia in Japanese prostate cancer patients treated with cabazitaxel

The present study aimed to evaluate the efficacy of cabazitaxel in Japanese patients affected by metastatic castration-resistant prostate cancer (mCRPC) previously treated with a docetaxel-containing regimen. In this retrospective study, 41patients with mCRPC treated with cabazitaxel at Keio University Hospital were retrospectively reviewed. Cabazitaxel at a dose of 20-25mg/m(2) was administered every 3 or 4weeks. Clinicopathological factors and laboratory data were collected to assess the prognostic factors for overall survival (OS) and progression-free survival (PFS). An upfront dose-reduction was required in 52.5% of patients due to their reduced general condition or advanced age. Prophylactic G-CSF was prescribed to all the patients. Grade 3 neutropenia and febrile neutropenia occurred in 21patients (53.6%) and 3patients (6.8%), respectively. Treatment was generally well tolerated, with a median of 5 cycles (range 1-17). Median PFS and OS from the start of cabazitaxel treatment were 4.4 and 15.0months (95% CI 8.9-21.2), respectively. Waterfall plot analysis revealed that a prostate-specific antigen (PSA) decline >50% was noticed in n=11 patients receiving cabazitaxel (26.8%). Univariate analysis revealed that poor performance status, PSA 100ng/mL prior to cabazitaxel treatment, visceral metastasis, absence of grade3/4 neutropenia during cabazitaxel therapy and neutrophil-lymphocyte ratio were significantly associated with shorter overall survival. Multivariate analysis revealed that poor performance status, visceral metastasis, and the absence of grade3/4 neutropenia during cabazitaxel therapy were the independent prognostic indicators for OS. The practical implication of our results might be to tailor cabazitaxel dosing on the basis of its hematological effects.