Short Course Radiation Treatment for Patients With Primary or Locally Recurrent Retroperitoneal Sarcoma Prior to Surgery

This study is testing short-course radiation therapy given before surgery for retroperitoneal sarcoma — a rare, aggressive soft tissue cancer that forms in the back of the abdominal cavity. The goal is to shrink the tumor before removing it surgically. **You may be eligible if...** - You are 18 or older - You have been diagnosed with a soft tissue sarcoma in the retroperitoneal space (deep abdominal area) - Your tumor is measurable on CT or MRI imaging - Surgery and radiation are both considered feasible based on imaging and specialist review - Your general health status is adequate (ECOG ≤2) **You may NOT be eligible if...** - You have a history of bowel obstruction, serious inflammatory bowel disease, or mesenteric ischemia - Your kidney function is impaired - Your tumor is not suitable for an R0 or R1 surgical resection - You do not meet the required performance status Talk to your doctor to see if this trial is right for you.