Ang, Daniel, Chan, Johan, Ong, Whee Sze, Tan, Hui Shan, Ng, Quan Sing, Yuen, John, Chen, Kenneth, Tay, Kae Jack, Wong, Siew Wei, Saad, Marniza, Nagata, Masayoshi, Horie, Shigeo, Chansriwong, Phichai, Ng, Chi-Fai, Wong, Alvin, Chua, Melvin L.K., Toh, Chee Keong, Tan, Min-Han, Lim, Tony, and Bhagat, Ali Asgar S.
PURPOSE: Androgen receptor splice variant 7 (ARV-7) is a resistance mechanism to hormonal therapy in metastatic castrate-resistant prostate cancer (mCRPC). It has been associated with poor outcomes. On progression to castrate resistance, ARV-7 positivity has been identified in global populations at an incidence of 17.8%-28.8%. Here, we characterize the incidence of ARV-7 positivity in Asian patients with mCRPC in a prospective fashion and evaluate its implications on treatment outcomes. METHODS: Patients with mCRPC from multiple centers in Southeast and East Asia were enrolled in a prospective manner before initiation of androgen receptor signaling inhibitors or docetaxel. ARV-7 status was evaluated at baseline with three commercially available assays: AdnaTest Prostate Cancer platform, Clearbridge method, and IBN method. Clinical outcomes at progression were assessed. The primary end point of this study was prevalence of ARV-7 positivity; secondary end points were incidence of ARV-7 positivity, prostate specific antigen (PSA) response rate, PSA progression-free survival (PFS), and overall survival (OS). RESULTS: A total of 102 patients with a median age of 72 years at enrollment participated. Overall, an incidence of ARV-7 positivity of between 14.3% and 33.7% in Asian patients with mCRPC was demonstrated depending on the assay used. Patients found to have ARV-7 positivity at enrollment had a numerically worse PSA PFS compared with ARV-7 negative patients. CONCLUSION: In this study, the incidence of ARV-7 positivity in Asian patients with mCRPC was shown to be similar to the global population. Patients with ARV-7 positivity appear to have more aggressive disease with numerically worse PSA PFS and OS. Further prospective studies are needed to fully characterize the relationship that ARV-7 positivity has on prognosis of Asian patients with mCRPC. AR-V7 expression is correlated with clinical outcomes post-treatment in large multicenter Asian mCRPC patient study. [ABSTRACT FROM AUTHOR]