Proton-Spatially Fractionated Radiotherapy and Standard Radiation Therapy for the Treatment of Newly Diagnosed Retroperitoneal Soft Tissue Sarcoma

This phase I/II trial studies the side effects and best dose of proton-spatially fractionated radiotherapy (P-SFRT) and to see how well it works with standard radiation therapy in treating patients with newly diagnosed retroperitoneal soft tissue sarcoma. Radiation therapy uses high energy x-rays, particles, or radioactive seeds to kill cancer cells and shrink tumors. Standard spatially fractionated radiotherapy (SFRT) refers to how the radiation is delivered to the tumor. SFRT means that different parts of the tumor are receiving different doses of radiation (fractionation) through beams that allow areas of higher and lower (peaks and valleys) of doses of the radiation. This spatial fractionation allows an overall high-dose radiation to be given in the peaks and those areas of the tumor may release cells and substances that may help with killing tumor cells, reducing tumor symptoms and shrinking tumors. Proton therapy is a type of radiation therapy that can overcome some of the barriers of standard SFRT. Protons are tiny radioactive particles that can be controlled in a beam to travel up to the tumor and, compared to the particles used in standard radiotherapy, proton therapy can deliver higher doses to the tumor because smaller doses of radiation are delivered to tissues away from the tumor. This allows radiation therapy dose-escalated (continuously increasing the dose of radiation) treatment to tumors even though the tumor is near radiation sensitive organs like the colon. Giving P-SFRT with standard radiation therapy may work better in treating patients with newly diagnosed retroperitoneal soft tissue sarcoma.