Phase II Study of Myeloablative Double Unit Umbilical Cord Blood Transplantation in Adult Patients

Inclusion Criteria: * Patients with hematologic malignancies requiring hematopoietic stem cell transplantation: (1) high risk acute myeloid leukemia in remission, (2) high risk acute lymphoblastic leukemia in remission, or (3) IPSS intermediate-2, high, or transfusion-dependent myelodysplastic syndrome * Patients who have suitable cord blood units for dUCBT * Patients with ECOG performance status 0-1 * Patients with adequate organ function: lung, kidney, liver, heart, etc. * Informed consent Exclusion Criteria: * Patients who can receive hematopoietic stem cell transplantation from HLA-matched sibling or unrelated donors * Patients who have anti-HLA antibodies * Patients with any evidence of central nervous system (CNS) involvement of disease * Patients with uncontrolled diabetes * Patients with uncontrolled hypertension * Patients with any evidence of active infection * Positive for human immunodeficiency virus (HIV) * Previous history of other malignancy within 5 years (Basal cell carcinoma of skin, cervical carcinoma in situ, and differentiated thyroid carcinoma with curative resection are permitted.) * Women who are pregnant or breastfeeding * Patients with previous history of allogeneic stem cell transplantation * Patients with major psychotic disorder or drug/alcohol abuser * Inappropriate patients according to the investigators' opinion