Intensified Azacitidine in High Risk Myelodysplastic Syndrome (MDS)

Inclusion Criteria: * MDS defined according to WHO classification (also including RAEB-T according to FAB classification) (see appendix 1) with intermediate-2 or high risk IPSS (see appendix 1). * Age ≥ 18 years and \<75 years. * Must understand and voluntarily sign an informed consent form. * Must be able to adhere to the study visit schedule and other protocol requirements. * Patients must have ECOG performance status (PS) of 0 - 2, and no major comorbidities preventing administration of an intensified regimen of azacitidine. * Women of child-bearing potential (i.e., women who are pre-menopausal or not surgically sterile) must : * Have a negative serum or urine pregnancy test within 2 weeks prior to beginning treatment on this study. Lactating patients are excluded. * Agree to use, and to be able to comply with, effective contraception without interruption, 4 weeks before starting study drug throughout the entire duration study drug therapy (including doses interruptions) and for 3 months after the end of the study drug therapy. * Male patients must : * Agree the need for the use of a condom if engaged in sexual activity with a woman of childbearing potential during the entire period of treatment, even if disruption of treatment and during 3 months after end of treatment. * Agree to learn about the procedures for preservation of sperm before starting treatment. * Creatinine \< 1.5 N or estimated clearance of creatinine above 30 ml/min. * Serum aspartate aminotransferase (AST)/serum glutamic-oxaloacetic transaminase (SGOT) or alanine transaminase (ALT)/serum glutamate pyruvate transaminase (SGPT) \< 3.0 x upper limit of normal (ULN). * Serum total bilirubin \< 1.5 mg/dL. (except for unconjugated hyperbilirubinemia due to Gilbert's disease or secondary to MDS-related dyserythropoiesis). * Health insurance Exclusion Criteria: * Patients with a history of myeloproliferative syndrome or CMML. * Known positive status for human immunodeficiency virus (HIV) or hepatitis B or C. * Pregnant and lactating patients are excluded because the effects of azacitidine on a fetus or a breast-fed child are unknown. * Uncontrolled intercurrent illness including, but not limited to uncontrolled infection, symptomatic congestive heart failure (NYHA \> II), cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements. * Patients receiving any other standard or investigational cytotoxic treatment for their hematologic malignancy in the last 8 weeks * Any medical condition which in the opinion of the investigator places the patient at an unacceptably high risk for toxicities of an intensified regimen of azacitidine. * Less than 6 months since prior allogeneic bone marrow transplantation. * Less than 3 months since prior autologous bone marrow or stem cell transplantation * Active cancer or prior history of malignancy other than MDS (except basal cell or squamous cell carcinoma or carcinoma in situ of the cervix or breast) unless the subject has been free of disease for ≥ 3 years. * Prior treatment with azacitidine. * Known allergy/intolerance to azacitidine or mannitol. * ECOG \> 2. * Life expectancy of less than 3 months.