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.