CT-guided Stereotactic Body Radiation Therapy and MRI-guided Stereotactic Body Radiation Therapy for Prostate Cancer, MIRAGE Study

PRIMARY OBJECTIVE: I. To determine whether (MRI)-guided stereotactic body radiotherapy (SBRT) improves acute physician-scored genitourinary (GU) toxicity when compared with standard computed tomography (CT)-guided SBRT for prostate cancer (PCa). SECONDARY OBJECTIVES: I. To determine whether there are differences in acute grade \>= 2 gastrointestinal (GI) toxicity as assessed by the Common Terminology Criteria for Adverse Events (CTCAE) version 4.03 scale, following MRI-guided SBRT versus CT-guided SBRT. II. To determine whether there are differences in 5-year cumulative incidences of late grade \>= 2 GU and GI physician-reported toxicity, following MRI-guided SBRT versus CT-guided SBRT. III. To quantify the temporal changes in patient-reported quality of life (QOL) outcomes, as assessed by the Expanded Prostate Cancer Index-26 (EPIC-26), International Prostate Symptom Scores (IPSS), and Sexual Health Inventory for Men (SHIM) QOL indices, following MRI-guided SBRT. IV. To determine whether there are differences in 5-year biochemical recurrence-free survival (BCRFS) following MRI-guided SBRT. V. To observe the proportion of SBRT fractions for which on-line adaptive radiotherapy is required due to changes in organ-at-risk anatomy. OUTLINE: Patients are randomized to 1 of 2 groups. GROUP I: Patients undergo 5 fractions of CT-guided SBRT over 14 days in the absence of disease progression or unacceptable toxicity. GROUP II: Patients undergo 5 fractions of MRI-guided SBRT over 14 days in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up every 3 months for 1 year, every 6 months for 4 years, and then yearly thereafter.