Busulfan and Fludarabine Before Donor Stem Cell Transplant in Treating Patients With Hematologic Cancer

OBJECTIVES: Primary * Determine the safety, in terms of treatment-related mortality at 100 days post-transplantation, of a myeloablative preparative regimen comprising busulfan and fludarabine and graft-vs-host disease (GVHD) prophylaxis comprising tacrolimus and methotrexate in patients with hematopoietic disorders undergoing matched unrelated donor stem cell transplantation. * Determine the efficacy, in terms of overall survival at 1-year post-transplantation, in patients treated with this regimen. Secondary * Determine organ toxicity in patients treated with this regimen. * Determine neutrophil and platelet recovery in patients treated with this regimen. * Determine the incidence and severity of acute and chronic GVHD in patients treated with this regimen. OUTLINE: * Myeloablative preparative regimen: Patients receive busulfan IV over 2 hours every 6 hours on days -7 to -4 and fludarabine IV over 30 minutes on days -7 to -3. * Allogeneic stem cell transplantation: Patients undergo allogeneic peripheral blood stem cell or bone marrow transplantation on day 0. Patients also receive filgrastim (G-CSF) subcutaneously daily beginning on day 7 and continuing until blood counts recover. * Graft-vs-host disease prophylaxis: Patients receive tacrolimus IV continuously beginning on day -2 and continuing until discharged from the hospital (may convert to oral dosing administered twice daily when tolerated) and methotrexate IV over 15-30 minutes on days 1, 3, 6, and 11. After completion of study therapy, patients are followed periodically. PROJECTED ACCRUAL: A total of 36 patients will be accrued for this study.