Figure 1. PRISMA flow chart eligibility criteria of articles included in meta-analysis. PubMed, EMBASE, CENTRAL and clinicaltrial.gov were selected to search articles between January 1990 and July 2020, using keyword “azacytidine or decitabine and myelodysplastic syndromes”. 1057 items were identified and 179 duplicate studies were removed. The remaining 896 studies were under title and abstract review. A total of 767 articles was excluded due to inappropriate type of study and uninterested intervention. 129 studies were retrieved to assess full text. 19 articles were included in this meta-analysis after depth review.