Dose Escalation Study Using Ultra-Hypofractionated, Image-Guided, Intensity-Modulated Radiotherapy in Prostate Cancer

Inclusion Criteria: Eligibility is not restricted to MSKCC to confirm biopsy/diagnosis. Participating institution testing is sufficient. * Low and intermediate risk prostate cancer patients will be eligible for this study. Risk groups will be assigned as per NCCN guidelines. * Low risk patients will be defined as: * PSA \< or = to 10 ng/ml and * Gleason score = 6 and * Clinical Stage \< or = to T2a * Intermediate risk patients will be defined as: * PSA 10-20 ng/ml or * Gleason score = 7 or * Clinical stage T2b/T2c Additionally, patients will be required to meet the following criteria: * Age \> or = to 18 * KPS \> or = to 70 * Pre-treatment endorectal coil MRI or CT (MRI preferred) at MSKCC showing no definite evidence of radiographic T3, T4, or N1 disease * Prostate size \< or = to 60 cc * International Prostate Symptom Score \< or = to 15 Exclusion Criteria: * Prior androgen deprivation therapy for prostate cancer * Elective pelvic lymph node irradiation * KPS \< 70 * Pelvic MRI or CT (MRI preferred) evidence of radiographic T3, T4 or N1 disease * Presence of distant metastasis as determined by: o alkaline phosphatase \> or = to ULN or * whole body bone scan positive for osseous metastases * Prior history of transurethral resection of the prostate * Prior history of chronic prostatitis * Prior history of urethral stricture * Prior history of pelvic irradiation * History of inflammatory bowel disease * Unable to give informed consent * Unable to complete quality of life questionnaires Abnormal complete blood count. Any of the following * Platelet count less than 75,000/ml * Hb level less than 10 gm/dl * WBC less than 3.5/ml * Abnormal renal function tests (creatinine \> 1.5)