PRIMORDIUM: This phase III trial is evaluating whether radiotherapy and LHRH agonist are a more effective treatment when also combined with apalutamide (hormone therapy) in people with prostate cancerA Randomized, Controlled, Multicenter, Open-label Study to Investigate the Efficacy and Safety of Adding Apalutamide to Radiotherapy and LHRH Agonist in High-Risk Patients With PSMA-PET-Positive Hormone-Sensitive Prostate Cancer, With an Observational Follow-up of PSMA-PET-Negative Patients

Inclusion

• Histologically confirmed adenocarcinoma of the prostate
• Previously treated with radical prostatectomy with or without lymph node dissection and either: a) for biochemical recurrence after radical prostatectomy (RP): any post-operative prostate-specific antigen (PSA) measurement of less than (<) 0.1 nanogram/milliliter (ng/mL) within 12 months after RP and without any PSA greater than and equal to (>=) 0.1 ng/mL within the 4 to 8-week period after RP or b) for persistent PSA after RP: PSA >=0.1 ng/mL within the 4 to 8-week period after RP, confirmed by additional measurement at least 3 weeks later
• Be able to swallow whole the study drug tablets or follow the instructions for admixing with apple sauce
• Results of the Prostate specific membrane antigen-positron emission tomography (PSMA-PET) at screening as determined by blinded independent, central review (BICR), must be: PSMA-PET-negative for any prostate cancer lesions (that is, no loco-regional lesion and no distant lesions); or PSMA-PET-positive for at least one loco-regional (pelvic) lesion without distant extra-pelvic lesion; or PSMA PET- positive for at least one loco--regional (pelvic) lesion with extra-pelvic lesion(s).
• High risk of developing metastasis defined as; a) for biochemical recurrence after RP: pathological Gleason score greater than or equal to (>=) 8 evaluated from prostate tissue specimen at radical prostatectomy, or prostate-specific antigen doubling time (PSADT) less than or equal to (<=) 12 months at the time of screening; b) for persistent PSA after RP: pathological Gleason score >=8, evaluated from prostate tissue specimen at radical prostatectomy
• Participants with evidence of distant metastasis on screening PSMA-PET scan must have no evidence of prostate cancer metastases on screening CT/MRI of the chest/abdomen/pelvis, Technetium 99m [99mTc] whole-body bone scan. Participants with a single bone lesion on 99mTc whole-body bone scan should have confirmatory imaging by CT or MRI; if the confirmatory scan confirms the bone lesion, the participant should be excluded from the study. Conventional images (99mTc-bone scan and CT/MRI) from the screening will be evaluated locally before randomization
• Eastern Cooperative Oncology Group Performance Status Grade 0 or 1