The sequential use of abiraterone and enzalutamide (MDV3100) in castrate resistant prostate cancer patients: Experience from Birmingham, United Kingdom.

Abstract

e16048 Background: Phase III studies have demonstrated survival benefits from abiraterone1 (Abi), and Enzalutamide2 (MDV3100; Enz) following disease progression in metastatic castrate resistant prostate cancer (mCRPC). Abi is available for treatment of mCRPC in the UK in patients previously treated with docetaxel. Enzalutamide (Enz) is available, via early access scheme, for progressive disease post docetaxel, regardless of prior Abi exposure. There has been no randomised trial on sequential usage of Enz post Abi. We therefore report our experience. Methods: We searched our pharmacy database for patients who have received Enz and identified 51 patients who started treatment between the 2nd August 2012 and 10thJanuary 2013. A detailed notes review was carried out of these patients. Results: Median age was 76 (range 55-87) years. All patients had received androgen deprivation therapy and Docetaxel. 46 patients had received previous Abi, 38 of patients’ receiving Abi as the last treatment prior to Enz. At the time of submission 10 patients had stopped Enz due to PSA progression with a mean TTP of 15 weeks (range 7-22) and 6 patients had died; 2 from disease progression (mean TTP 3.5 weeks). For the 30 patients still on Enz, the mean duration of treatment was 16.47 weeks (range 4-27). 33 patients didn't report any significant side effects associated with Enz treatment. The most common side effect was fatigue (23.6%); 3 patients (6%) experiencing G3 fatigue. Other reported side effects included diarrhoea (4%), nausea (6%), confusion (6%), anxiety (6%), depression (6%), hallucinations (2%) and insomnia (2%). 3 patients (6%) had Enz stopped due to G3 fatigue. Conclusions: The AFFIRM study demonstrated TTP of 8.3 months (36 weeks) in patients post-docetaxel2. In this audit the TTP of patients receiving Enz post-Abi was 15 weeks, suggesting possible reduced efficacy in patients receiving Enz post-Abi and docetaxel. However, longer follow-up of the 30 patients currently taking Enz is required. The number of patients experiencing G3 fatigue was the same as reported in AFFIRM, but there were a surprising number of patients experiencing psychiatric side-effects.