OBJECTIVES:~Primary Phase~Determine the best dose of treosulfan when administered with fludarabine as a reduced-intensity conditioning regimen followed by allogeneic hematopoietic stem cell transplantation, in terms of incidence of severe to fatal toxicity to major organ systems and incidence of graft failure, in patients with acute myeloid leukemia, lymphoblastic leukemia, or myelodysplastic syndrome.~Secondary Phase~Determine the safety of this regimen, in terms of incidence of grade II-IV acute and chronic graft-versus-host disease, in these patients.~Determine, preliminarily, the efficacy of this regimen, in terms of incidence of relapse, overall and disease-free survival, donor chimerism on days 28 and 100, and incidence of 200-day and 1-year nonrelapse mortality, in these patients.~Determine the pharmacokinetic and pharmacodynamic profile of treosulfan in patients treated with this regimen.~OUTLINE: This is a multicenter, dose-finding study of treosulfan.~Reduced-intensity conditioning: Patients receive treosulfan IV over 2 hours on days -6 to -4 and fludarabine IV over 30 minutes on days -6 to -2.~Cohorts of 5-10 patients receive escalating/de-escalating doses of treosulfan until the best dose is determined among the 3 pre-selected doses. The best dose is defined as the dose preceding that at which 4 of 10 patients experience dose-limiting toxicity.~Allogeneic hematopoietic cell transplantation (AHCT): Patients undergo allogeneic bone marrow or peripheral blood stem cell transplantation on day 0.~All male patients with acute lymphoblastic leukemia OR male patients with acute myeloid leukemia who have prior or current testicular involvement receive external-beam radiotherapy to the testicles before AHCT.~After completion of study treatment, patents are followed periodically.~PROJECTED ACCRUAL: A total of 60 patients will be accrued for this study.
RATIONALE: Drugs used in chemotherapy, such as treosulfan and fludarabine, work in different ways to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. Giving treosulfan and fludarabine together with a donor bone marrow transplant or a peripheral stem cell transplant may be an effective treatment for acute myeloid leukemia, acute lymphoblastic leukemia, or myelodysplastic syndrome.~PURPOSE: This phase II trial is studying giving treosulfan together with fludarabine to see how well it works in treating patients who are undergoing a donor stem cell transplant for acute myeloid leukemia, acute lymphoblastic leukemia, or myelodysplastic syndrome.