Abstract： Objective To evaluate the efficacy and safety of dose-reduced decitabine for the lower risk myelodysplastic syndrome (MDS) patients with transfusion dependent.Methods Twenty-five cases of lower risk (low or intermediate-1 risk in IPSS risk group) MDS patients with transfusion dependence from November 2009 to September 2012 were treated by dose-reduced decitabine (20 mg/m2 intravenously once daily for 3 days).And their efficacy,side effects,quality-of-life and survival rate were evaluated.Results Among them,the responses included complete remission (CR,n =3,12％),transfusion independence (n =4,16％),hematologic improvement (HI,n =8,32％) and stable disease (SD,n =2,8％).And the overall response rate (ORR) was 68％ (17/25).Among 11 cases available for cytogenetic evaluation,1 achieved partial cytogenetic remission (PRc).Ⅳ grade hematologic toxicity rate was 48％ (12/25) and Ⅲ-Ⅳ grade infection rate 20％ (5/25).No severe hematologic toxicity was observed.After treatment,the Karnofsky performance score (KPS) increased from 47 ± 16 to 66 ± 22 (P =0.001) ; more patients were reclassified as WPSS ≤1 (44％vs 16％,P=0.031) or MDACC score ≤7 (64％ vs 8％,P=0.022).The median follow-up time was 467(14-881) d.The 100 and 600-day expected survive rates of low and intermediate-1 risk in IPSS risk group were 100％ versus 95.2％ and 100％ versus 90.5％.Conclusions Dose-reduced decitabine is well-tolerated and effective in transfusion dependent MDS patients in IPSS-lower risk.There is a low rate of severe hematologic toxicity and early mortality.It may prolong their survival time.