The purpose of this study is to evaluate the effect of various clinical variables including HLA-disparity and NK cell-related variables, upon outcomes of allogeneic hematopoietic cell transplantation (HCT) using uniform conditioning regimen including busulfan, fludarabine, and antithymocyte globulin (ATG) in patients with acute myeloid leukemia (AML) in the first complete remission (CR). The donors for allogeneic HCT include HLA-matched siblings, matched unrelated donors, and haploidentical family donors.

Therefore, the endpoints of the study are engraftment, secondary graft failure, acute and chronic graft-versus-host disease (GVHD), immune recovery, infections, leukemia recurrence, non-relapse mortality, and relapse-free (RFS) and overall survival (OS) of patients.

Inclusion Criteria:

• Patients with non-promyelocytic AML (intermediate-risk or high-risk diseases by NCCN guideline 2016) in the first CR
• Patients should be 16 years of age or more and 75 years of age or less
• The performance status of the patients should be 70 or over by Karnofsky performance scale
• Patients should have adequate hepatic function (bilirubin less than 2.0 mg/dl, AST less than three times the upper normal limit)
• Patients should have adequate renal function (creatinine less than 2.0 mg/dl)
• Patients should have adequate cardiac function (ejection fraction > 40% on MUGA scan)
• Patients and stem cell donors must sign informed consent
• For hematopoietic cell donor, if a patient has an HLA-matched sibling (65 years or younger), that sibling will be a cell donor. If a patient does not have an HLA-matched sibling but an HLA-A, B, C, DRB1 7-8/8 matched unrelated donor, the unrelated donor will be a cell donor. If a patient has neither HLA-matched sibling nor unrelated donor, an HLA-haploidentical familial donor will be a cell donor.

This is a single center, observational study in a patient population with non-promyelocytic AML who have achieved complete remission after induction chemotherapy. The patients will be enrolled consecutively.