Cabazitaxel in metastatic castrate resistant prostate cancer (mCRPC) in the era of enzalutamide (ENZA) and abiraterone acetate (AA).

Abstract

e16517 Background: The concurrent development of cabazitaxel, AA, ENZA, and radium-223 has recently increased the number of therapeutic options for mCRPC. Cabazitaxel is currently approved for mCRPC patients who have previously received docetaxel. There are no data on the activity of cabazitaxel in patients who had previously progressed on docetaxel and either ENZA or AA. We examined the efficacy and tolerability of cabazitaxel in patients who progressed on docetaxel and either AA or ENZA. Methods: We searched our databases for all mCRPC patients who had received cabazitaxel up to July 2016. We reviewed medical records to collect information on tolerability, treatment sequencing and treatment outcomes. These data were analysed descriptively using Excel 2010. Results: Of 30 patients screened, only 20 patients received cabazitaxel after progressing on docetaxel and either ENZA or AA. The median age at the time of treatment was 70.8 years. All except one patient had Zubrod performance status (PS) ≥1. All patients had ≥4 sites of metastatic disease, 20% had liver or lung metastases. About 11/20 (55%) individuals had previously received ENZA (median duration 5.8 months) and 12/20 (60%) received AA (median duration 10 months). The median number of cabazitaxel administered was 6 cycles. Only 3/20 (15%) completed 10 cycles. The most common reasons for treatment discontinuation were progressive disease (35.3%) and toxicity (23.5%). The dose of cabazitaxel was reduced at baseline in most patients due to poor PS. PSA response occurred in one-third of patients while stable disease (clinical+radiological) was seen in 40% patients. The median progression free survival (PFS) was 4 months and overall survival measured 4.6 months. About 20% had ≥6 months PFS. After progression, only one-fourth went on to receive further systemic therapy. The most common toxicities were anaemia (100%), neutropenia (65%), fatigue (65%), peripheral neuropathy (35%) and diarrhoea (25%). Conclusions: Within limitations of a small retrospective study, cabazitaxel showed very modest antitumour activity in this cohort of mCRPC patients with significant tumour burden and prior exposure to docetaxel and biological agents.