Study To Examine Toxicity Of Allogeneic Stem Cell Transplantation For Relapsed Or Therapy Refractory Ewings Sarcoma

Inclusion Criteria:

1. Patients aged 0-30 years with relapsed or therapy refractory ES, excluding patients with brain metastases. Patients who have received a prior autologous stem cell transplant are eligible.
2. 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:

1. Organ dysfunction: Patients who have the following levels of organ system dysfunction are not eligible:

   * Cardiac: Ejection Fraction \< 50 %
   * Renal: Est. Creatinine Clearance \< 50\*
   * Hepatic: Bilirubin \> 3.0
   * Pulmonary: DLCO \< 70 %, or for patient who cannot cooperate with pulmonary function testing, O2 saturation \< 95 % on room air.
   * Performance status: Lansky performance \< 70; ECOG status \> 2 \*this is based on the Schwartz formula for children less than 18 years of age, and the Cockcroft - Gault formula, for those \> 18 years.\[21, 22\]
2. Patients with an isolated local recurrence of their tumor (in the site of the primary tumor) \> 1 year after completing therapy are excluded, as these patients could be cured with local therapy alone.

3 As a 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 HIV may be rejected as candidates for transplantation, based on the clinical judgment of the stem cell transplant physician