The purpose of this study is to determine the efficacy and safety of combined ATG #antithymocyte globulin # regimen (5mg/kg divided from day -5 to day -2) for aGVHD(acute graft-versus-host disease ) prophylaxis in matched sibling donor peripheral blood stem cell transplantation (MSD-PBSCT).

Transplantation with G-CSF #Granulocyte colony stimulating factor #mobilized peripheral blood stem cell (PBSCT) has been a stable transplant setting with matched sibling donor transplantation. Unmanipulated haploidentical donor PBSCT (haplo-PBSCT) has been applied in patients with hematologic malignancies. In our previous cohort study, haplo-PBSCT was associated with lower incidence of severe acute GVHD and extensive chronic GVHD compared with matched sibling donor PBSCT (MSD-PBSCT). Haplo-PBSCT has the same GVHD prophylaxis regimen with MSD-PBSCT, except ATG. It suggested the potential advantage of ATG in prophylaxis of GVHD and improvement of long term quality of life of the transplant recipients, which motivate us to observe the efficacy of combined ATG regimen for GVHD prophylaxis in MSD-PBSCT.

Inclusion Criteria:

• Patients were aged from 14 to 65 years;
• Patients were diagnosed of acute leukemia or MDS;
• There were indications of MSD-PBSCT for these patients;
• Patients without any uncontrolled infections or without severe pulmonary, renal, hepatic or cardiac diseases.

Exclusion Criteria:

• Patients with any uncontrolled infections or with severe pulmonary,renal, hepatic or cardiac diseases;
• AML patients with t (15;17).