A Phase I-II Dose Escalation Study of Stereotactic Body Radiation Therapy in Patients With Localized Prostate Cancer

Inclusion Criteria: * All patients must be willing and capable to provide informed consent * Histologic confirmation of prostate adenocarcinoma * T2-T3 tumors, N0 (clinically by no evidence of metastatic lymph nodes on CT or MRI) * No direct evidence of regional or distant metastases * PSA less than or equal to 50 μg/ml * Visible gross tumor at the prostate endorectal coil MRI. * The ultrasound or MRI based volume estimation of the patient's prostate gland no greater than 70g or 70cc * No significant urinary obstructive symptoms; IPSS score must be ≤ 15 (alpha blockers allowed) * Patient must have undergone an endorectal coil magnetic resonance image (MRI) of the prostatic gland (before rectal spacer if any), * Patient must have undergone the following assessments in case of PSA ≥ 20μg/L, and/or T3 tumor and/or Gleason Score ≥ 8: * bone scan * Chest abdominal and pelvis computed tomography (CT) scan * If tumor is localized at less than 3 mm from the rectum a rectal spacer is mandatory. Patient accepts the rectal spacer to be injected before treatment starts * Patient accepts to have one planning MRI after the injection of rectal spacer (without endorectal coil) * Patient accepts the preparation of the bladder (bladder full), before the planning MRI, planning CT and then before each treatment fraction Exclusion Criteria: * Previous radiotherapy in the pelvis * Tumor localized at less than 3 mm from the urethra * History of inflammatory colitis (including Crohn's disease and ulcerative colitis) * Prior cancer in the pelvis * Any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule; those conditions should be discussed with the patient before inclusion in the trial