No more datas about post-transplant cyclophosphamide (PT/Cy) used in pediatric refractory acute myeloid leukemia (R-AML）patients. Investigators reasoned that this group of patients if they have been treated with ablative conditioning regimens for HSCT combined with PT/Cy, under the rapid of immune reconstitution will have better outcomes.

Haploidentical stem cell transplantation (HSCT) is a potentially curative therapy for patients with high risk or refractory acute myeloid leukemia (R-AML). Graft-versus-host disease （GVHD）is a major barrier to achieve success for patients with HSCT. High dose cyclophosphamide given after HLA-matched related and unrelated allogeneic stem cell transplantation for patients with hematologic malignancies is effective single agent (GVHD) prophylaxis in adults and in pediatric benign patients. Data describing outcomes for pediatric maligant patients has not been reported. Investigators have recruited 26 pediatric patients (3 years < age <18 years) between March 2015 to July 2018 with primary induction R-AML treated in investigators' institution for R-AML with modified myeloablative regimen, post-transplant cyclophosphamide (PTCy) has been used as GVHD prophylaxis.

Conditioning regimen of the group of patient consisted Idrabine(IDA,10mg/m2/day) which was administered intravenously for 2 days, from days -14 to -13, total body irritation (TBI, 9 Gy) which was divided into 3 fractions and 3 days from -12 to -10, thymoglobulin (2.5mg/kg/day) was administered for 3 days, from -9 to -7, etoposide (VP-16, 300mg/m2) which was infused intravenously on day -6, cladribine (10mg/m2/day) which was administered for 3 days from -5 to -2 .

Inclusion Criteria:

-refractory AML

Exclusion Criteria:

- complete remission AML