Treosulfan, Fludarabine Phosphate, and Total-Body Irradiation Before Donor Stem Cell Transplant in Treating Patients With High-Risk Acute Myeloid Leukemia, Myelodysplastic Syndrome, Acute Lymphoblastic Leukemia

PRIMARY OBJECTIVES: I. Decrease the incidence of relapse to \< 15% at 6 month post transplant in patients with high risk acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) transplanted from related or unrelated donors, without unacceptably increasing toxicity (10% non-relapse mortality \[NRM\] at 6 months). SECONDARY OBJECTIVES: I. Evaluate the incidence of NRM at 180 days and 1 year after hematopoietic cell transplantation (HCT). II. Evaluate overall survival (OS) and relapse-free survival (RFS). III. Incidence of grades II-IV acute graft-versus-host disease (GVHD). IV. Incidence of chronic GVHD. V. Donor chimerism on days +28 and +100. OUTLINE: CONDITIONING REGIMEN: Patients receive fludarabine phosphate intravenously (IV) over 30 minutes on days -6 to day -2 and treosulfan IV over 2 hours on days -6 to day -4. Patients also undergo total-body irradiation on day 0. TRANSPLANTATION: Patients undergo allogeneic peripheral blood stem cell transplantation or bone marrow transplantation on day 0. GVHD PROPHYLAXIS: Patients receive tacrolimus IV continuously or orally (PO) twice daily (BID) on days -1 to 56, followed by a taper until day 180 in the absence of GVHD. Patients also receive methotrexate IV on days 1, 3, 6, and 11. After completion of study treatment, patients are followed up periodically.