Response to cabazitaxel in CRPC patients previously treated with docetaxel and abiraterone acetate.

Abstract

155 Background: Cabazitaxel, which is a tubulin-binding chemotherapy, and the CYP-17 androgen biosynthesis inhibitor abiraterone acetate (AA) are both approved for patients with metastatic castration resistant prostate cancer (CRPC) following docetaxel chemotherapy. Recent preclinical data suggest that taxanes impact AR signalling and could imply cross-resistance between new AR targeting treatments and taxane chemotherapy. The aim of this study is to evaluate the antitumor activity of cabazitaxel after AA. Methods: We retrospectively evaluated antitumor activity of cabazitaxel in patients (pts) with metastatic CRPC and progressive disease after docetaxel and AA. Radiological response by RECIST, PSA response by PCWG2 criteria and symptomatic benefit were examined. Results: 89 pts were treated with third-line cabazitaxel, after docetaxel (median 8 cycles; range: 4-12), and AA (median duration of treatment 4.8 months, range: 1-55 months). At cabazitaxel initiation median age was 68 years (range: 53-83), ECOG performance status was 0 or 1 in 70% of pts, and median PSA was 309 ng/ml (range: 3.75-9150). Bone, lymph node and visceral metastases were present in 80 pts (89%), 37 pts (41%), and 12 pts (13%) respectively. An average of 6 cycles of cabazitaxel (range 1-15) were administered. All pts had PSA data available and 44 (49%; 95% CI 39-60%) had a 50% or greater PSA decline. In the 35 pts with RECIST evaluable disease, 7 (20%; 95% CI 8-37%) had a partial response. Conclusions: In men with metastatic CRPC cabazitaxel appears to retain activity in the third-line setting following docetaxel and AA.