Decitabine+Cladribine+Cytarabine+Granulocyte Colony-stimulating Factor (D-CLAG) for Relapsed or Refractory Acute Myeloid Leukemia (AML)

Inclusion Criteria:

* Acute myeloid leukemia (non-acute promyelocytic leukemia) must be diagnosed before enrollment. Diagnostic criteria refer to WHO (World Health Organization) classification.
* Refractory or relapsed AML: refractory is defined as the failure of CR after 2 courses of standard induced remission therapy (2 courses of idarubicin+cytarabine (IA) regimen or 1 course of IA regimen + 1 course of high dose cytarabine); Relapse is defined as the blast cells \>5% in bone marrow or presence of extramedullary leukemia for patient who achieved CR before.
* Age 18-70.
* Eastern cancer cooperation group (ECOG) ≤2.
* Creatinine clearance ≥30 mL/min (estimated glomerular filtration rate (eGFR) according to the Cockcroft-Gault formula or Modification of Diet in Renal Disease (MDRD) formula).
* Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤3× upper limit of normal range (ULN), total bilirubin ≤2×ULN.
* Echocardiography (ECHO) showed left ventricular ejection fraction (LVEF)≥50%.
* Life expectancy \>8 weeks.
* Voluntarily sign the informed consent and understand and comply with the requirements of the study.

Exclusion Criteria:

* White blood cell (WBC) \> 50 \* 109 / L
* Patients who have received salvage treatment with D-CLAG.
* Current active cardiovascular disease, such as uncontrolled arrhythmia, uncontrolled hypertension, congestive heart failure, any grade 3 or 4 heart disease according to the New York heart association (NYHA) functional classification, or a history of myocardial infarction within 6 months prior to screening.
* Other serious diseases that may limit patient participation in the trial (e.g. progressive infections, uncontrolled diabetes).
* Pregnant or nursing women.
* Unable to understand or follow the research protocol or unable to sign the informed consent.