This is a prospective, open-label, phase II trial with 1:1 randomization to either Arm A biomarker directed therapy (patients with ctDNA fraction <2% receive enzalutamide, and ctDNA fraction ≥2% receive docetaxel), versus Arm B clinician's choice of enzalutamide or docetaxel, in subjects with metastatic castration-resistant prostate cancer post abiraterone. At time of progression, patient will cross-over to the other therapy (e.g., enzalutamide to docetaxel, and docetaxel to enzalutamide).
The purpose of this study is to assess the strategy in treatment selection using ctDNA fraction as a predictive biomarker to direct treatment decision (ctDNA fraction <2% receives enzalutamide, and ctDNA fraction ≥2% receives docetaxel) versus clinician's choice of enzalutamide or docetaxel, in subjects with metastatic castration-resistant prostate cancer post abiraterone setting.