This study is testing if the drug *apalutamide* can improve the usual treatment for prostate cancer. Prostate cancer is a disease where cells in the prostate grow out of control. After surgery, patients usually receive hormone therapy and radiation to fight cancer. **Apalutamide** is a drug that may help stop cancer by blocking male hormones, which fuel cancer growth, from attaching to cancer cells. This study has two groups: one gets the usual treatment, and the other gets the usual treatment plus apalutamide. **Key Points:** - The study requires taking *apalutamide* pills every day for 8 cycles, with each cycle lasting 90 days. - Participants will have follow-up visits every 6 months for three years, then once a year after that. - Eligibility includes being 18 years or older, having recovered from prostate surgery, and meeting specific health conditions. Patients will also undergo different scans and blood tests throughout the study to check their health and how well the treatment works. Participants should not join other clinical trials during this study.