• The primary objective is to evaluate the response rate (Complete response plus partial response) of decitabine (to be assessed at every 2nd cycle).
  

• Safety (including adverse events and clinical lab results) and tolerability should be evaluated throughout the study at each visit.
  

This is an open-label, multicenter, single-arm study in Taiwan. The recommended decitabine dose is 20mg/m² administered intravenously over 1 hour, once daily for 5 consecutive days, of a 4-week cycle. The dose can be reduced, delayed, or discontinued by the investigators if certain toxicities occur. Responses to decitabine are sometimes only observed after multiple courses of treatment. Therefore, to maximize a patient's chance to respond, a patient whose disease has not progressed and who is tolerating the treatment, should receive at least 8 cycles of decitabine. If, in the opinion of the treating physician, there is continued clinical benefit from the treatment, absence of progressive disease and absence of unacceptable toxicity, at the time the patient reaches 8 cycles, treatment can be continued beyond 8 cycles, as long-term extension phase treatment. Any patient who achieves a complete remission should be treated for at least 2 more cycles after first documentation of CR (Complete Response), after which treatment can be discontinued. In case of relapse, off-treatment after prior CR, re-treatment with decitabine is allowed, and can be considered at the discretion of the treating physician. The information collected in the long-term extension phase and at time of re-treatment will be summarized separately. Response to treatment will be based on International Working Group (IWG) 2006 response criteria.Safety will be assessed by the monitoring of adverse events, physical examinations, vital signs measurements, hematology and clinical chemistry tests. The study will include patients diagnosed with myelodysplastic syndrome (according to WHO classification, but including patients with Bone Marrow blast counts of 20-30% for whom no progression was observed during a 1 month observation period), both de novo or secondary, and including previously treated and untreated patients. Eligible subjects must sign an informed consent and meet all inclusion criteria and have none of the exclusion criteria. The secondary objectives are to evaluate the safety and tolerability of decitabine, hematologic improvement, cytogenetic response rates, time to acute myeloid leukemia progression or death, overall survival, transfusion requirements and transfusion independence, duration and reasons for hospitalization and quality of life assessment.

The recommended decitabine dose is 20mg/m² administered intravenously over 1 hour, once daily for 5 consecutive days of a 4-week cycle. To maximize a patient's chance to respond, a patient whose disease has not progressed and who is tolerating the treatment, should receive at least 8 cycles of decitabine.