Treatment of Patients With Myelodysplastic Syndrome or Acute Myelocytic Leukemia With an Impending Hematological Relapse With Azacitidine (Vidaza)

Inclusion Criteria: Screening: * signed informed consent * Age ≥18 years * patients with MDS or AML after conventional chemotherapy or allogeneic HSCT and positive molecular marker such as t(6,9), NPM1 pos. or CD34+ or CD117+ in the case of an allogeneic HSCT Treatment: * MDS or AML without haematological relapse (blasts \<5% in the bone marrow), and * decrease of CD34 donor chimerism (\<80%) after allogeneic related or unrelated HSCT in CD34+ or CD117+ MDS or AML or * increase in the AML-specific molecular marker in the quantitative PCR for t(6,9), NPM1+ AML \>1% after conventional chemotherapy or allogeneic HSCT or * persistence of the (above) MRD levels \>1% (relative to the reference gene) after conventional chemotherapy or allogeneic HSCT * leukocytes \> 3 Gpt/l and platelets \>75 Gpt/l (transfusion independent) Exclusion Criteria: * Known history of hypersensitivity to any of the drugs used or their constituents or to drugs with similar chemical structure, * Participation of the patient in another clinical trial within the last 4 weeks before the inclusion * addiction or other disorders that do not allow the concerned person, to assess the nature and scope and possible consequences in the clinical investigation * pregnant or breast feeding women * women of childbearing potential, except women who meet the following criteria: * post-menopausal (12 months natural amenorrhea or 6 months amenorrhea with serum FSH \>40 U/ml) * postoperative (6 weeks after hysterectomy with or without bilateral ovariectomy ) * regular and proper use of a contraceptive method with error rate \<1% per year (e.g., implants, depot injections, oral contraceptives, intrauterine device, IUD) during study treatment and up to 1 year after completion of therapy * sexual abstinence during study treatment and up to 1 year after completion of therapy * Vasectomy of the partner * Men who do not use one of the following types of effective contraception during study treatment and up to 1 year after completion of therapy: * sexual abstinence * State post-vasectomy * Condom * Evidence that the participating person is not expected to comply with the protocol (such as lack of cooperation) * Uncontrolled active infection * Severe hepatic impairment (AST and ALT may not exceed three times the normal) or liver cirrhosis or malignant liver tumor * Dialysis dependent renal dysfunction * Known severe congestive heart failure, incidence of clinically unstable cardiac or pulmonary disease These criteria are not for the screening phase up to a known allergic reaction to azacitidine or intolerance to apply.