Magnetic Resonance-Guided Stereotactic Body Radiation Therapy for the Treatment of Prostate Cancer

PRIMARY OBJECTIVE: I. To determine the safety of performing focal MR-guided SBRT. SECONDARY OBJECTIVES: I. To assess the tolerability of focal MR-guided SBRT. II. To characterize changes in urinary, bowel and sexual function in patients receiving focal MR-guided SBRT. III. To characterize changes in prostate symptoms in patients receiving focal MR-guided SBRT. IV. To characterize changes in sexual health in patients receiving focal MR-guided SBRT. V. To estimate the rate of biochemical recurrence after receiving focal MR-guided SBRT. VI. To estimate the rate of in-field prostate recurrence after receiving focal MR-guided SBRT. VII. To estimate the rate of out-of-field prostate recurrence after receiving focal MR-guided SBRT. VIII. To estimate the rate of salvage therapy after receiving focal MR-guided SBRT. IX. To estimate the time to local radiographic progression after receiving focal MR-guided SBRT. X. To estimate the time to distant radiographic progression after receiving focal MR-guided SBRT. EXPLORATORY OBJECTIVES: I. To characterize changes in imaging features from pre-treatment to post-treatment, assessed using multiparametric prostate MRI (including T2 weighted imaging, apparent diffusion coefficient (ADC) values, and dynamic contrast-enhanced (DCE) perfusion metrics, as well as radiomic features, and prostate-specific membrane antigen positron emission tomography (PSMA PET) imaging, if available. II. To characterize the intraprostatic tumor microenvironment and clonal dynamics following focal SBRT using surveillance biopsy tissue obtained at 2 years post-treatment, with comparison of cores sampled within versus outside the radiation field. OUTLINE: Patients undergo five treatment fractions of MR-guided SBRT over 30-45 minutes each up to three times a week (TIW) over approximately 2 weeks in the absence of disease progression or unacceptable toxicity. Patients also undergo MRI and biopsy throughout the study as well as computed tomography (CT) on study. After completion of study treatment, patients are followed up at 90 days, 12 months, and then every 6 months for 4 years.