Reduction of Gastrointestinal Toxicity in Prostate Cancer by Proton Spot Placement

This purpose of this study is to examine the placement of proton spots during pencil beam scanning proton therapy for low and intermediate risk prostate cancer. The researchers will test a unique technique called "Spot Delete" to control the placement of spots during treatment planning. They will also use a special computer model to study how the energy of the proton beam (linear energy transfer) is related to rectal and bladder side effects. The study involves creating a treatment plan based on a CT scan, which helps guide the proton beam in the body. The clinical team uses this CT scan to find the best placement for the protons. The "Spot Delete" method prevents protons from stopping in the rectum, sigmoid, and small bowel, which is thought to be related to acute or late toxicities, such as tenesmus, diarrhea, fecal incontinence, proctitis, and rectal hemorrhage.