RecruitingDrug trialDFMO Maintenance for Patients With Relapsed/Refractory Ewing Sarcoma or OsteosarcomaThe purpose of this study is to determine the feasibility of administering DL-alpha-difluoromethylornithine (DFMO) to patients with relapsed Ewing sarcoma and osteosarcoma who have completed all planned therapy and have no evidence of disease.