Salvage Moderate Hypofractionated Versus Ultrahypofractionated Radiotherapy for Biochemical Recurrence After Radical Prostatectomy in Prostate Cancer

Inclusion Criteria: * Patients who have undergone radical prostatectomy for prostate cancer * Age ≥ 20 years * Persistent prostate-specific antigen (PSA) elevation after radical prostatectomy, defined as prostate-specific antigen (PSA) levels of 0.1-1.0 ng/mL with at least three consecutive increases * Patients who have undergone prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) for evaluation of prostate-specific antigen (PSA) elevation * Good performance status (ECOG performance status 0-1) Exclusion Criteria: * Radiologic or clinical evidence of gross local recurrence, lymph node metastasis, or distant metastasis, including findings on prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT), as determined by the treating physician * Presence of lymph node metastasis or distant metastasis at the time of radical prostatectomy * History of prior pelvic radiotherapy * Diseases associated with a high risk of radiation toxicity (e.g., inflammatory bowel disease, systemic lupus erythematosus, scleroderma, or other connective tissue diseases) * History of another malignancy diagnosed or recurrent within the past 3 years (except for skin cancer and thyroid cancer) * Uncontrolled acute or chronic conditions deemed inappropriate for study participation by the investigator (e.g., dementia, Alzheimer's disease, cerebral infarction, etc.)