Single Arm Trial of Preoperative Stereotactic Body Radiation Therapy (SBRT) for T3a or Gleason Grade Group 4 Prostate Cancer

This study involves Stereotactic Body Radiation Therapy (SBRT) followed by prostatectomy (removal of the prostate). SBRT is a relatively new radiation technique in which a few doses of radiation are delivered to small, well-defined tumors. It has been used effectively in other cancers like lung and liver. The radiation will be given for only 5 days. The purpose of this study is to compare the effects, good and/or bad, of different doses of SBRT given before prostatectomy.