The purpose of this prospective, open-label, randomized multicenter study is to evaluate the safety and efficacy of low dose decitabine in combination with modified BUCY vs modified BUCY as a myeloablative conditioning regimen for high-risk patients with acute myeloid leukemia (AML) undergoing allogeneic hematopoietic stem cell transplantation (Allo-HSCT).

Allo-HSCT is the most effective treatment stratagey for high risk acute myeloid leukemia. At present, modified BUCY is the standard conditioning regimen for AML undergoing allo-HSCT in our institute. However, relapse occured in as high as 30-50% high risk AML patients after allo-HSCT. Thus, the best conditioning regimen for this subgroup remains to be optimized. Low dose decitabine in combination with chemotherapy have been shown to improve comple remission rate of high risk AML patients. To reduce the relapse rate after allo-HSCT, low dose decitabine is added in the modified BUCY regimen. In this study, the safety and efficacy of low dose decitabine + modified BUCY vs modified BUCY myeloablative conditioning regimens in high risk undergoing allo-HSCT are evaluated.

Inclusion Criteria:

• Age 12 to 60 years.
• Diagnosis of high-risk acute myeloid leukemia at the time of transplant. ("High-risk" AML features are defined by the following: relapsed or primary refractory AML; Secondary AML（AML Secondary to myelodysplastic syndrome(MDS) or treatment-related AML); extramedullary leukemia; adverse cytogenetic abnormalities of monosomy 5, monosomy 7, or deletion of 5q; or presence of FLT3 positive internal tandem duplication (FLT3/ITD+), particularly high allelic ratio.)
• Patient must have adequate pre-transplant organ function.

Exclusion Criteria:

• Age <12 or >60 years.
• Uncontrolled bacterial, viral, fungal, or other infection before conditioning regimen.
• Any other severe concurrent diseases, or have a history of serious organ dysfunction.
• Pregnant or lactating females.