A Phase I Study to Examine the Toxicity of Allogeneic Stem Cell Transplantation for Relapsed or Therapy Refractory Ewing Sarcoma

Inclusion Criteria: * Patients aged 0-30 years with relapsed or therapy refractory Ewings sarcoma, excluding patients with brain metastases. Patients who have received a prior autologous stem cell transplant are eligible. * Related and unrelated marrow and peripheral blood stem donors must be 9/10 or 10/10 (HLA A, B, C, DR, DQ) matched with the recipient. Exclusion Criteria: * Organ dysfunction: Patients who have the following levels of organ system dysfunction are not eligible: * Cardiac: Ejection Fraction less than 50 percent * Renal: Est. Creatinine Clearance less than 50 * Hepatic: Bilirubin greater than 3.0 * Pulmonary: Diffusing Capacity for Carbon Monoxide (DLCO) less than 70 percent, or for patient who cannot cooperate with pulmonary function testing, O2 saturation less than 95 percent on room air. * Performance status: Lansky performance less than 70; Eastern Cooperative Oncology Group (ECOG) status greater than or equal to 2 * Patients with an isolated recurrence of their tumor (in the site of primary tumor) greater than 1 year after completing therapy are excluded as these patients could be cured with local therapy alone. * As part of the standard of care for pre-transplant evaluation subjects will be tested for exposure to viral agents such as hepatitis B, C, HTLV-1/2 and HIV. Subjects testing positive for HI may be rejected as candidates for transplantation, based on the clinical judgement of the stem cell transplant physician.