• Frederik Birkebaek Thomsen, Martin Andreas Røder, Per Rathenborg, Klaus Brasso, Michael Borre, and Peter Iversen.
• Department of Urology, Copenhagen Prostate Cancer Center, Rigshospitalet, Copenhagen University Hospital , Copenhagen , Denmark ; Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark.
• Scand J Urol. 2014 Jun 1; 48 (3): 268-75.

ObjectiveThe 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 MethodsTwenty-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.ResultsAll 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.ConclusionsPrevious 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.

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