This study is for people aged 18 and older with a type of cancer called retroperitoneal liposarcoma. This cancer is in the fat cells in the back part of the tummy area. The study wants to see how well treatments work when the cancer comes back after surgery. Doctors might suggest surgery again, or surgery with radiation (RT) and maybe chemotherapy. The study lasts for 5 years, and during this time, patients will answer some questions about how they feel. These questions take about 15-20 minutes each time.

• The study lasts for 5 years and includes answering some questions about quality of life several times.
• Participants must have had their cancer removed once before and meet certain health criteria.
• Women who can have babies need a negative pregnancy test before starting the study.