Combination Chemotherapy and Antithymocyte Globulin in Reducing Graft-Versus-Host Disease in Patients Undergoing Donor Stem Cell Transplantation For Myelodysplastic Syndrome or Myeloproliferative Disorder

OBJECTIVES: * Determine the incidence of acute graft-vs-host disease (GVHD) requiring therapy in patients with myelodysplastic syndromes or myeloproliferative disorders treated with busulfan, cyclophosphamide, and anti-thymocyte globulin prior to transplantation with filgrastim (G-CSF)-mobilized peripheral blood stem cells (or bone marrow) from related or unrelated donors. * Determine the incidence of relapse and relapse-free survival in patients treated with this regimen. * Determine the incidence of non-relapse mortality by day 100 and 1 year posttransplantation in patients treated with this regimen. * Determine the incidence of Epstein-Barr virus reactivation, infections, and chronic GVHD in patients treated with this regimen. OUTLINE: This is a dose-escalation study of anti-thymocyte globulin. * Conditioning and graft-vs-host disease (GVHD) prophylaxis: Patients receive oral busulfan every 6 hours on days -7 to -4 (16 doses), cyclophosphamide IV on days -3 and -2, and anti-thymocyte globulin IV over 3 hours on days -3, -2, and -1. Cohorts of 15 patients receive adjusted doses of anti-thymocyte globulin to determine the optimal dose at which Epstein-Barr virus (EBV) activation and GVHD are reduced. The optimal dose is the dose at which 2 consecutive cohorts receive the same regimen. * Stem cell transplantation: Patients undergo peripheral blood stem cell (PBSC) or bone marrow transplantation on day 0. * Posttransplantation GVHD prophylaxis: Patients receive cyclosporine IV continuously on days -1 to 4 and then orally twice daily until day 180. Patients also receive methotrexate on days 1, 3, 6, and 11. Patients are followed every 6 months for 2 years and then annually thereafter. PROJECTED ACCRUAL: A total of 30-45 patients will be accrued for this study within 2 years.