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, 41 patients with mCRPC treated with cabazitaxel at Keio University Hospital were retrospectively reviewed. Cabazitaxel at a dose of 20‐25 mg/m² was administered every 3 or 4 weeks. 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 21 patients (53.6%) and 3 patients (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 15.0 months (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 ≥100 ng/mL prior to cabazitaxel treatment, visceral metastasis, absence of grade 3/4 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 grade 3/4 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.