The purpose of this study is to determine if we lower the chance of your prostate cancer growing or spreading by adding the drug relugolix to the usual radiation therapy? This study seeks to find if this approach is better or worse than standard of care for prostate cancer.

Treatment and follow up for this study may be up to 5 years. The procedures include blood samples, PET scans, hormone therapy and radiation therapy. Risks include diarrhea, back pain, weight gain, and headache. You may or may not receive a direct benefit from participating in this trial, however, information learned from the trial may help other people in the future.