The efficacy of enzalutamide for castration-resistant prostate cancer (CRPC) patients with intraductal carcinoma of the prostate (IDC-P).

Abstract

209 Background: Enzalutamide (ENZ) was approved to prolong survival for castration-resistant prostate cancer (CRPC) patients before and after chemotherapy. No factor was identified to predict the effectiveness of ENZ so far. .Intraductal carcinoma of the prostate (IDC-P) was newly recognized on 2017 EAU guideline and considering as a poor prognostic factor、although there has been no reports to predict the therapeutic effects of ENZ according to the presence of IDC-P. In this study, we evaluated the efficacy of ENZ for CRPC patients with or without IDC-P. Methods: We retrospectively identified 199 CRPC patients treated with ENZ from 2014 to 2018 in author-affiliated hospitals. All needle biopsy slides were reviewed by a single genitourinary pathologist and IDC-P was defined according to the criteria of McNeal at initial biopsy. Endpoint is overall survival (OS) from the time of CRPC diagnosis and time to treatment failure of ENZ. PSA response is defined as over 50% PSA decline from baseline. Results: The median patient age was 71 (range, 49–90) years. The median initial PSA was 154 ng/ml (range, 3.9–24736 ng/ml). The patients who received docetaxel were 42/199 (21%). IDC-P was detected in 98 patients (49%) at initial prostate biopsy. PSA response was 70.5% in patients without IDC-P and 53.9% in patients with IDC-P. The median OS from the time of CRPC was 37.9 and 71.5 months with and without IDC-P, respectively (P=0.013). There was no significant difference on OS in CRPC patients with IDC-P between before and after docetaxel (P=0.941). Same result was observed in CRPC patients without IDC-P (P=0.86). In time to treatment failure by ENZ, patients with IDC-P showed worse prognosis than patients without IDC-P after docetaxel (P=0.068). On the other hand, the difference disappeared before docetaxel regardless the presence of IDC-P (P=0.94). Conclusions: IDC-P is a poor prognostic factor for CRPC patients treated with ENZ. ENZ may be most effective for CRPC patients with IDC-P before chemotherapy.