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CAST: A retrospective analysis of cabazitaxel and abiraterone acetate sequential treatment in patients with metastatic castrate-resistant prostate cancer previously treated with docetaxel
Wissing MD, Coenen JL, van den Berg P, Westgeest HM, van den Eertwegh AJ, van Oort IM, Bos MM, Bergman AM, Hamberg P, Ten Tije AJ, Los M, Lolkema MP, de Wit R, Gelderblom H
Int J Cancer. 2015 Mar 15;136(6):E760-72. doi: 10.1002/ijc.29231. Epub 2014 Oct 3.
Cabazitaxel and abiraterone have both received approval for treating metastatic castrate-resistant prostate cancer (mCRPC) patients after first-line docetaxel therapy. In the cabazitaxel and abiraterone sequential treatment (CAST) study, the clinical outcome of docetaxel-treated mCRPC patients treated sequentially with both cabazitaxel and abiraterone was studied. Data were collected retrospectively from mCRPC patients at 12 hospitals across the Netherlands who initiated cabazitaxel and/or abiraterone before December 2012. Primary outcome measure was overall survival (OS); secondary measures were progression-free survival (PFS), biochemical PFS, and best clinical and PSA response. Hospital admission data during treatment were collected, as well as toxicities resulting in treatment discontinuation or patient death. Sixty-three and 69 patients received Cab→Abi (cabazitaxel prior to abiraterone) and Abi→Cab before July 10th, 2013, respectively. Median OS was 19.1 months and 17.0 months in Cab→Abi and Abi→Cab treated patients, respectively (p = 0.369). Median PFS and biochemical PFS were significantly longer in Cab→Abi treated patients: 8.1 versus 6.5 (p = 0.050) and 9.5 versus 7.7 months (p = 0.024), respectively. Although partial responses to cabazitaxel occurred in both groups, Abi→Cab treated patients had a significantly decreased antitumor response from cabazitaxel than Cab→Abi treated patients (median PFS 5.0 versus 2.6 months, p < 0.001). Minor differences in toxicities were observed based on therapy sequence; generally, toxicity from cabazitaxel could be severe, while abiraterone toxicity was milder. This retrospective analysis indicates that primary progression on cabazitaxel or abiraterone did not preclude a response to the other agent in mCRPC patients. However, tumor response of both agents, particularly cabazitaxel, was lower when administered as higher-line therapy in the selected study population.