Magnetic Resonance Guided Focal Stereotactic Body Radiation Therapy for Localized Prostate Cancer

Inclusion Criteria:

Patients must have a histologically confirmed diagnosis of adenocarcinoma of the prostate
Patient must have a history/physical examination with digital rectal examination of the prostate within 90 days prior to screening
Eastern Cooperative Oncology Group (ECOG) performance status must be level 0 or 1 within 60 days prior to registration
Patient must have a histological evaluation of the prostate biopsy with assignment of a Gleason score to the biopsy material; Gleason scores ≤ 7(3+4)
Serum creatinine ≤ 1.5 times upper limit of institutional normal (normal: ≤ 1.17 mL/min/1.73 m^2)
Clinical stage a ≤ T1-T2a (American Joint Committee on Cancer [AJCC] 7th edition)
Prostate specific antigen (PSA) ≤ 10 ng/mL within 90 days prior to registration; PSA should not be obtained within 10 days after prostate biopsy
Subjects must have the ability to understand and the willingness to sign a written informed consent document
Patient willing and able to complete the Expanded Prostate Cancer Index Composite (EPIC) questionnaire (baseline, 6, 12 and 24 months post end of radiation therapy)
Patients must be able to undergo an MRI with contrast
Bone scan completed within 90 days

Exclusion Criteria:

Evidence of distant metastases
Regional lymph node involvement
Previous radical surgery (prostatectomy), cryosurgery, or high intensity focused ultrasound (HIFU) for prostate cancer
Previous pelvic irradiation, prostate brachytherapy, or bilateral orchiectomy
Previous hormonal therapy, such as luteinizing hormone-releasing hormone (LHRH) agonists (e.g., goserelin, leuprolide) or LHRH antagonists (e.g., degarelix), anti-androgens (e.g., flutamide, bicalutamide), estrogens (e.g., diethylstilbestrol [DES]), or surgical castration (orchiectomy)
Use of finasteride within 30 days prior to registration; PSA should not be obtained prior to 30 days after stopping finasteride
Use of dutasteride within 90 days prior to registration; PSA should not be obtained prior to 90 days after stopping dutasteride
Previous or concurrent cytotoxic chemotherapy for prostate cancer
Severe, active co-morbidity, defined as follows:
Unstable angina and/or congestive heart failure requiring hospitalization within the last 6 months
Transmural myocardial infarction within the last 6 months
Acute bacterial or fungal infection requiring intravenous antibiotics at the time of registration
Chronic obstructive pulmonary disease exacerbation or other respiratory illness requiring hospitalization or precluding study therapy at the time of registration
Hepatic insufficiency resulting in clinical jaundice and/or coagulation defects; note, however, that laboratory tests for liver function and coagulation parameters are not required for entry into this protocol; (patients on Coumadin or other blood thinning agents are eligible for this study)
Acquired immune deficiency syndrome (AIDS) based upon current Centers for Disease and Control (CDC) definition; note, however, that human immunodeficiency virus (HIV) testing is not required for entry into this protocol; protocol-specific requirements may also exclude immuno-compromised patients
Patients unable to undergo an MRI with contrast