This pilot clinical trial studies magnetic resonance (MRI)-guided focal stereotactic radiosurgery (SRS) in treating patients with low- or intermediate-risk localized prostate cancer. Stereotactic radiosurgery may be able to send x-rays directly to the tumor and cause less damage to normal tissue.

PRIMARY OBJECTIVES:

I. Evaluate the correlation of histopathology findings in comparison to regions of the prostate reported to be suspicious for harboring tumor burden on multiparametric MRI report/s.

II. Demonstration of the dosimetric and radiobiological advantages of focal stereotactic body radiation therapy (SBRT) versus whole-gland radiation therapy.

III. Evaluation of clinical outcomes in focal SBRT for localized prostate cancer.

OUTLINE:

Patients undergo 3 fractions of MRI-guided focal SRS every other day for 1 week. Patients undergo additional MRI scans between the 2nd and 3rd fractionated treatments, at 6 months following the end of radiation therapy, and at 12 and 24 months.

After completion of study treatment, patients are followed up every 3 months for up to 24 months.

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