Previous prostate cancer surgery or pelvic radiation.

Prior/concurrent systemic chemotherapy for prostate cancer.

Active inflammatory bowel disease (Crohn's disease, diverticulitis or ulcerative colitis) affecting the rectum.

History of hip replacement.

Prior intrapelvic surgery.

Taking Saw Palmetto or methotrexate and unable or unwilling to discontinue its uses during radiation.

Receiving continuous and current anticoagulation with Warfarin sodium (Coumadin), Clopidogrel bisulfate (Plavix), dabigatran etexilate mesylate (Pradaxa),enoxaparin sodium (Lovenox), or aspirin/er dipyridamole (Aggrenox).

Hypofractionated Proton Radiation Therapy for Low and Intermediate Risk Prostate Cancer

What this study is about