Activity of Cabazitaxel After Docetaxel and Abiraterone Acetate Therapy in Patients With Castration-Resistant Prostate Cancer

The efficacy of cabazitaxel (CAB) after abiraterone acetate (AA) in metastatic castration-resistant prostate cancer (mCRPC) is unknown. Because both affect the androgen receptor (AR) there is a concern about the activity of this sequence. We retrospectively demonstrated a prostate-specific antigen (PSA) response of 31.5%, partial response of 15.3%, and median survival of 8.2 months with CAB. CAB was active after AA and docetaxel in mCRPC. Background: Cabazitaxel and AA have been approved by the US Food and Drug Administration for use after docetaxel in mCRPC. Recently, CAB appeared to be active when given after AA. AA is capable of inducing AR splice variants that confer ligand-independent AR transactivation. Because microtubule-targeting agents impair AR nuclear transport and activity, we raised concerns about CAB efficacy after AA failure in mCRPC. Patients and Methods: One hundred thirty mCRPC patients received AA after docetaxel treatment in compassionate programs. Of them, 24 (18.4%) subsequently received CAB. We retrospectively reviewed their data using conventional methods. Results: Twenty-four patients received a median of 4 (range, 1-13) CAB cycles. Nineteen (79.1%) of them received primary prophylaxis with growth factors. Median patient characteristics were: age 65 (range, 57-85) years; Gleason score: 8 (range, 6-10); and PSA: 128.1 (range, 0.01-1700) ng/mL. A PSA response (>= 50% decrease from baseline) occurred in 6 (31.5%) of 19 evaluable patients (95% confidence interval [CI], 11.8-54.2%). CAB therapy obtained a partial response in 2 of the 13 (15.3%) evaluable patients (95% CI, 2.9-45.4%). Median survival from initiation of CAB was 8.2 (95% CI, 3.34-13.05) months, from AA 16.1 (95% CI, 11.56-20.64) and from docetaxel 32.0 (95% CI, 11.56-39.69). Conclusion: A limited number of patients with mCRPC received CAB after docetaxel and AA treatment. In this selected population, CAB was active. (C) 2014 Elsevier Inc. All rights reserved.