Stereotactic Body Radiation Therapy in Treating Patients With Localized Prostate Cancer That Have Undergone Surgery

PRIMARY OBJECTIVES: I. To determine the efficacy of postoperative stereotactic body radiation therapy (SBRT) at a dose of 34 grays (Gy) in five fractions, as compared with historical control efficacy rates in patients who received conventionally fractionated postoperative radiotherapy. II. To determine the toxicity of postoperative SBRT at a dose of 34 Gy in five fractions, both via physician-scored and patient-reported metrics. SECONDARY OBJECTIVES: I. To determine the proportion of SBRT fractions for which on-line adaptive radiotherapy is required due to changes in organ-at-risk anatomy, in the subset of patients treated with magnetic resonance imaging (MRI)-guided radiotherapy. II. To gather biomarkers that may elucidate predictors of increased efficacy or increased toxicity. TERTIARY OBJECTIVES: I. To compare toxicity profiles (both physician-scored and patient-reported) between patients treated utilizing a linear accelerator versus a tri-60Co teletherapy platform. OUTLINE: Patients undergo SBRT every other day (QOD) for 14 days. Patients may also receive androgen deprivation therapy (ADT) comprised of a luteinizing hormone-releasing hormone agonist or a gonadotropin-releasing hormone antagonist, and an oral anti-androgen for 6 months at the discretion of the treating physician. After completion of study treatment, patients are followed up at 1 month, every 3 months for 1 year, every 6 months for 4 years, and then annually thereafter.