This is a randomized, double-blind, placebo-controlled, multicenter study of apalutamide plus GnRH agonist compared with GnRH agonist among participants with high-risk, localized or locally advanced prostate cancer receiving primary radiation therapy (RT). The study will include a Screening Phase, Treatment Phase, a Posttreatment Phase, and a Long-term Follow-up Phase. Participants will either receive either apalutamide (experimental) or bicalutamide 50 milligram (mg) capsule plus placebo as control group. Safety will be monitored throughout the study.
The purpose of this study is to determine if apalutamide plus gonadotropin releasing hormone (GnRH) agonist in participants with high-risk, localized or locally advanced prostate cancer receiving primary radiation therapy results in an improvement of metastasis-free survival.