Treatment Patterns after Abiraterone Acetate in Patients (pts) with Metastatic Castration-Resistant Prostate Cancer (mcrpc): Post Hoc Analysis of COU-AA-302.

168 Background: Treatment patterns of mCRPC have changed substantially in the last few years. In COU-AA-302 (chemotherapy-naïve men with mCRPC), abiraterone acetate plus prednisone (AA) significantly improved radiographic progression-free survival and overall survival vs placebo plus prednisone (P). There is limited information about treatment patterns after AA. In this post hoc analysis of pts in the AA treatment arm who progressed, we characterized subsequent therapy after pts discontinued study drug. Methods: In COU-AA-302, 546 pts were randomized and received AA. Treatment patterns of pts receiving ≥ 1 subsequent therapy for mCRPC after progressing on AA were collected retrospectively and source verified. Results: As of March 2014, 8% (44/546) of pts continued on AA; 67% (365/546) received ≥ 1 subsequent therapy for mCRPC. 36% (194/546) and 15% (83/546) of pts had ≥ 2 and ≥ 3 subsequent therapies, respectively. 80% (435/543) of pts in the P arm had ≥ 1 subsequent therapy. Most frequent subsequent therapy in AA pts was taxane chemotherapy (docetaxel [DOC], cabazitaxel [CBZ]), androgen signaling–directed therapy (AA, enzalutamide [ENZ], ketoconazole [KETO]), and immunotherapy (sipuleucel-T [SIP-T]) (Table). Among AA pts who received DOC as first subsequent therapy, median age was 69 years; median duration of DOC post-AA (n = 261) was 3 months (IQR: 0.95-5.7); and PSA progression was the most common reason for discontinuation. Among AA pts with baseline PSA and ≥ 1 post-baseline PSA value, 40% (40/100) had ≥ 50% PSA decline (27/100 confirmed responses) with first subsequent DOC chemotherapy. Conclusions: This post hoc analysis indicates that treatment with subsequent therapy was common (67% and 80%) in pts with chemotherapy-naïve mCRPC who progressed with AA or P, respectively. PSA decline suggests antitumor activity in pts who progressed with AA and received subsequent DOC. Despite limitations of a retrospective analysis, these data support further assessment of subsequent therapy following AA treatment for mCRPC. Clinical trial information: NCT00887198. [Table: see text]