Comparison of Alternative Androgen Receptor-axis-targeted Agent (ARATA) and Docetaxel as Second-line Therapy for Patients With Metastatic Castration-resistant Prostate Cancer With Progression After Initial ARATA in Real-world Clinical Practice in Japan.

Abstract

The objective of the present study was to assess the oncologic outcomes of patients receiving second-line therapy against metastatic castration-resistant prostate cancer (mCRPC). The present study included 222 consecutive mCRPC patients with progression during initial androgen receptor-axis-targeted agent (ARATA) therapy with either abiraterone acetate (AA) or enzalutamide (Enz). Of these 222 patients, 108 subsequently received an alternative ARATA (AA-to-Enz, n= 49; Enz-to-AA, n= 59) and 114 received docetaxel (DTX; AA-to-DTX, n= 54; Enz-to-DTX, n= 60). The prostate-specific antigen (PSA) level in the 114 patients receiving DTX was significantly greater than that in the 108 patients receiving ARATA. However, no significant differences were found in the remaining parameters between the 2 groups. The PSA response rate, PSA progression-free survival (PFS), and overall survival (OS) during second-line therapy in the DTX group (n= 114) were significantly superior to those for the ARATA group (n= 108; PSA response rate, 42.1% vs. 21.3%; median PSA PFS, 7.2 vs. 4.2months; median OS, 17.5 vs. 14.5 months). Similar trends were confirmed by comparing these outcomes among 4 therapy groups, with significant differences (PSA response rate, Enz-to-AA vs. AA-to-DTX and Enz-to-AA vs. Enz-to-DTX; PSA PFS, AA-to-Enz vs. Enz-to-AA, AA-to-Enz vs. AA-to-DTX, Enz-to-AA vs. AA-to-DTX, and Enz-to-AA vs. Enz-to-DTX; and OS, Enz-to-AA vs. AA-to-DTX and Enz-to-AA vs. Enz-to-DTX). Furthermore, the introduction of DTX was independently associated with improved PSA PFS, but not OS, on multivariate analysis. Favorable oncologic outcomes can be expected with DTX treatment, rather than with alternative ARATA, for mCRPC patients after failure of an initial ARATA.