Proton or Photon RT for Retroperitoneal Sarcomas

While being screened to determine eligibility for this study you may choose to participate in an additional blood sample for circulating DNA and a genomic DNA sample. Since we are looking for the highest dose of Radiation Therapy that can be administered safely without severe or unmanageable side effects in participants that have retroperitoneal sarcomas, not everyone who participates in this research study will receive the same dose of study therapy. The dose you get will depend on the number of participants who have been enrolled in the study before you and how well they have tolerated their doses. Your study doctor will tell you which dose you will get. Radiation planning is standard of care for all patients undergoing radiation therapy. Before you begin radiation therapy you will have a radiation planning CT scan of the tumor site. This scan will be in addition to the scans done in order to confirm your eligibility for this study. Doctors will use teh images from this scan to plan your radiation treatment. You will receive radiation therapy every day Monday through Friday for about six weeks. You will receive study therapy as an outpatient. During radiation therapy, you will be seen by the study doctor once a week. Each visit will take about 15 minutes, and the following assessments will be completed: medical history, vital signs, body weight and assessments for any side effects you may be experiencing. After the final dose of radiation therapy you will be assessed for side effects of radiation following your last dose and before surgery. The following assessments will be completed before your surgery at this visit: Chest CT, CT/MRI of the abdomen/pelvis and routine blood tests to check for overall health. You will be seen for a follow-up visit within one month of discharge following surgery and again four months after the surgery. At the first follow-up visit, the following assessment will be completed: medical history, vital signs and body weight, questions about side effects and routine blood tests to check for overall health. At the four month follow up visit the following assessment will be completed: medical history, vital signs and body weight, chest CT and abdominal/pelvic CT. After your four month follow-up visit, you will be seen twice yearly following radiation for the first five years and then once a year for the rest of your life.