Postdocetaxel treatment for castrate-resistant prostate cancer: The sequential use of abiraterone and cabazitaxe.

Abstract

234 Background: Large phase III trials have shown both abiraterone (Abi) and cabazitaxel (Cbz) to have a survival benefit in patients with metastatic castrate resistant prostate cancer (mCRPC). They are now used routinely throughout the UK in this setting. The mechanisms of resistance of these drugs remain unclear and therefore, their sequential use is less recognised. We present data from patients who have been exposed to both therapies. Methods: In this retrospective study, we searched our own pharmacy databases to identify all patients that had been exposed to both Abi and Cbz. All patients were treated between April 2009 and October 2012. A total of 21 patients were reviewed and clinical data was collected. SPSS software was used to create Kaplan Meier curves. Results: 17 of the 21 patients received Abi before Caz. Median progression free survival for patients on the sequential regimes was 16.9 months (95% Confidence interval: 10.5-23.3). Reviewing the drugs individually found progression free survival was 5.1 months (4.4-6.0 months) with Abi and 7.1 months (5.1-9.1) with Cbz. Conclusions: In a select group of patients who are fit enough to receive both drugs, superior progression free survival is seen than can be expected on one drug alone. The data compares favourably to that seen in the TROPIC study where time to progression on Cbz was 2.8 months. Furthermore, lack of response to one drug did not preclude worthwhile response to the other agent. These findings are consistent with the drugs having separate mechanisms. At this stage the series is not mature enough to draw conclusions on survival benefit. An updated series, involving larger patient numbers, will be presented at the meeting.