Enzalutamide treatment in patients with metastatic castration-resistant prostate cancer progressing after chemotherapy and abiraterone acetate

Abstract

Objective. The aim of this study was to record prostate-specific antigen (PSA) response and overall survival (OS) for a group of metastatic castration-resistant prostate cancer (mCRPC) patients treated with enzalutamide following progression after abiraterone treatment in the post-chemotherapy setting. Material and methods. Twenty-four mCRPC patients with progression after abiraterone treatment following primary docetaxel therapy received enzalutamide 160 mg/day. The percentage PSA response was recorded following first line docetaxel, abiraterone and enzalutamide treatment. Fischer's exact test, Mann–Whitney U test and linear regression model were used to test for differences in PSA response. Results. All patients had a follow-up of at least 3 months. The median PSA response following 1 month of enzalutamide was –12% (range –56% to 76%), while the median best PSA response was –22% (–76% to 76%). Forty-six percent had a greater than 30% decrease in PSA. The PSA response to enzalutamide did not correlate with the number of prior cancer treatments (p = 0.57), time from diagnosis to mCRPC (p = 0.11) or prior response to docetaxel (p = 0.67). However, patients treated with second line cabazitaxel had an inferior PSA response to enzalutamide (p = 0.03), and there was a trend for the PSA response to abiraterone to correlate with the PSA response to the succeeding enzalutamide (B = 0.22, p = 0.05). The median OS was 4.8 months. Conclusions. Previous abiraterone therapy is associated with a less marked fall in PSA following enzalutamide therapy in post-chemotherapy mCRPC patients compared with reported results in randomized trials. Larger prospective studies of sequencing are warranted.

Key Words::

• abiraterone
• castration-resistant prostate cancer
• enzalutamide
• post-chemotherapy
• sequencing

Acknowledgements

We thank clinical research nurse Stine Thim and Birgit Kaa Bach for assistance with data collection.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.