DFMO Maintenance for Patients With Relapsed/Refractory Ewing Sarcoma or Osteosarcoma

This study is testing whether a drug called DFMO (difluoromethylornithine) — an oral medication that may help prevent cancer from coming back — can keep Ewing sarcoma or osteosarcoma (two types of bone cancer) in remission in young patients who have already finished treatment for a relapse and currently have no evidence of disease. **You may be eligible if...** - You are under 40 years old - You have been diagnosed with relapsed Ewing sarcoma or osteosarcoma - You have completed all planned treatment for your relapse and currently have no detectable cancer - Your blood counts, kidney function, and liver function are within the required ranges **You may NOT be eligible if...** - Your cancer has not yet been treated or is still detectable - You are 40 years old or older - Your blood counts or organ function tests do not meet the required thresholds Talk to your doctor to see if this trial is right for you.