Myelodysplastic syndrome (MDS) is a malignant clonal disorder of the hematopoietic system characterized by ineffective hematopoiesis, peripheral hematocrit and a high risk of transformation to acute myelocytic leukemia (AML). According to the international prognostic scoring system (IPSS) approximately 30% of patients die from leukemic transformation and 70% die from refractory hematocrit. In patients with high-risk MDS (intermediate-risk-2 or high-risk IPSS), given the high risk of transformation to AML, the goal of treatment is to reduce the risk of transformation to AML and prolong survival, while in patients with low-risk MDS (low- or intermediate-risk-1 IPSS), the main goals of treatment are to improve hematocrit, to move away from transfusion dependence, to improve quality of life and to prolong survival. Decitabine (5-aza-2’deoxycytidine), a nucleotide analogue and specific inhibitor of DNA methylation, induces DNA demethylation as well as hematopoietic cell differentiation. Standard doses of decitabine (20 mg.m-2.d-1 x 5 days) are associated with a high degree of myelosuppression, a high risk of infection and bleeding, and, as MDS is mostly seen in elderly patients, and low-risk MDS patients are even more affected by iron overload due to long-term transfusion dependence, which affects patients’ organ function and thus reduces their tolerance to standard dose decitabine therapy. By counting the causes of death in 273 low-risk MDS patients receiving only supportive care from 1980 to 2004, Dayyani et al. found that MDS-related deaths (including infection, bleeding, conversion to AML, and disease progression) occurred in 84% of patients, with infection, bleeding, and conversion to AML accounting for 38%, 13%, and 14% of deaths, respectively. Cardiovascular events accounted for 44% of non-MDS-related deaths. Infection, bleeding, and cardiovascular events are all complications of hematocrit and transfusion dependence; therefore, improving the degree of hematocrit and moving away from transfusion dependence are the primary goals of treatment for patients with low-risk MDS. Anemia is an important factor affecting the quality of life (QoL) of low-risk MDS patients, and about 50% of MDS patients have symptoms of anemia. The efficacy of erythropoietin (Epo) is influenced by the level of serum Epo and the degree of transfusion dependence. Serum Epo levels <100 U/L, 100-500 U/L and >500 U/L were assigned scores of +2, +1 and -3, respectively, and mean transfusions <2 U/month and ≥2 U/month were assigned scores of +2 and -2. The final total scores of >+1, -1 to +1 and <-1 were 74%, 23% and 7% effective for Epo treatment, respectively. Patients with serum Epo >200 U/L and transfusion dependency had a low response rate to Epo, and there are very limited therapeutic options for this group of patients. In addition to the heavy financial burden of prolonged transfusion, the consequent iron overload affects the overall survival time of MDS patients and enhances the risk of conversion to AML by increasing the damage of DNA strands by reactive oxygen radicals, which, together with their direct effect on vital organs. 0.001; P = 0.003). Although iron removal therapy can be administered in conjunction with blood transfusion, iron removal is a long-term process, and the expense and adverse effects of iron removal administration affect patient compliance and reduce patient quality of life. Hematologic improvement (HI) has been shown to prolong survival in patients with AML and high-risk MDS. The study was conducted in 99 patients who survived but did not achieve CR or CRp (CR but incomplete platelet recovery) from 2000 to 2006, of whom 32 achieved HI (HI duration was not required), and of the 32, 14 had HI duration ≥ 4 weeks and 13 had HI duration ≥ 8 weeks. Finally, HI duration ≥ 4 weeks and ≥ 8 weeks were found to improve survival in patients with AML and high-risk MDS (p=0.01, p=0.01). Although there is no clear data on the role of HI and detachment from transfusion in prolonging the survival of low-risk MDS patients, since hematocrit and transfusion dependence are the two most important factors affecting survival time and quality of life in low-risk MDS patients, resolving this paradox will certainly contribute to the survival of low-risk MDS patients. For patients with low-risk MDS, transfusion dependence, or concomitant severe hematocrit, are equally suitable candidates for demethylating drug therapy, but with different therapeutic goals and actual acceptable toxicity than for high-risk MDS. Decitabine is approved for MDS above intermediate-risk 1 in the IPSS and of course includes all patients with the FAB subtype. To achieve the goal of weaning patients with low-risk MDS from component blood transfusions, improving quality of life, and reducing myelosuppression to minimize the risk/benefit ratio, we explored the use of reduced-dose decitabine (20 mg.m-2.d-1 IV infusion for 3 consecutive days) for treatment of selected patients with low-risk MDS. In this study, 25 patients with low-risk MDS were enrolled, 3 (12.0%) achieved CR, 4 (16.0%) were discharged from component blood transfusion, 8 (32.0%) achieved HI, 2 (8.0%) achieved SD, and the ORR reached 68.0%. Of 11 patients with feasible cytogenetic evaluation, 1 (9.1%) achieved PRc. Garcia-Maneroe previously reported low-dose decitabine (20 mg.m-2.d-1 x 3d and 20 mg/m2 once weekly for 4 weeks) for low-risk MDS patients with CR rates of 9% and 0, and PR (partial remission) rates of 6% and 5%, respectively. mCR (myeloid complete remission) rates were 0 and 5%, HI was 2% and 0%, SD (stable disease) was 47% and 73%, and ORR was 64% and 83%, respectively. The ORR results of our study were similar to those reported abroad, and none of the CR rates were high, but reduced doses of decitabine did significantly improve transfusion dependence in patients with low-risk MDS. Among 99 patients with MDS treated with standard dose decitabine reported by Steensma et al, the incidence of grade III-IV neutropenia, thrombocytopenia, febrile neutropenia and anemia were 31.0%, 18%, 14% and 12%, respectively, and the incidence of grade III-IV pneumonia was 11%, and the incidence of grade III-IV nausea and vomiting were all 1%. 11 cases (11 %) patients died within 30 days after receiving standard doses of decitabine. In our study, the incidence of grade III-IV hematologic toxicity was 48.0%, the incidence of grade III-IV infection was 20.0%, there was no grade III-IV bleeding, severe nausea and vomiting (grade III-IV) or hepatic impairment (grade III-IV), and one (4.0%) patient experienced early death (death within 4 weeks of treatment). Reduced doses of decitabine reduced the incidence of grade III-IV hematologic toxicity and early death. The 1-year expected survival rates were reported to be 88% and 80% for the IPSS score low-risk and intermediate-risk-1 groups, respectively, and the 2-year expected survival rates were 82% and 65%, respectively, and the 1-year expected survival rates after treatment with reduced-dose decitabine were 100% and 90.5% for the low-risk and intermediate-risk-1 groups, respectively, in this study. The expected survival rates at 600 days after standard-dose decitabine treatment were 100% and 55% in the low-risk and intermediate-risk-1 groups, respectively, and the expected survival rates at 600 days after reduced-dose decitabine treatment were 100% and 90.5% in the present study. Thus, reduced-dose decitabine significantly improved the prognosis and prolonged survival of low-risk and intermediate-risk-1 patients with IPSS scores, and its effect was no less than, or even better than, that of standard-dose decitabine. It is worth pointing out that the IPSS prognostic score, which is calculated based on the patient’s primal cell ratio, hematocrit and cytogenetic alterations, is simple and easy to use and is now widely used. The WPSS score is based on WHO staging, transfusion dependence and cytogenetic alterations, and can be used at any time during disease treatment. In contrast to the WPSS score, the MDACC score eliminates the influence of individual subjectivity of transfusion dependence on the score. Given that we studied transfusion-dependent MDS, we analyzed the scores of this group of transfusion-dependent low-risk MDS before and after treatment with reduced-dose decitabine using both the WPSS score and MDACC score when using the IPSS score. The IPSS score was used to score 84.0% (21 cases) of those at low risk as intermediate to high risk MDS by the reWPSS score, however, 33.3% (7 cases) of these high risk group were transferred to the low risk group after treatment. For those at low risk with IPSS scores 72.0% (18 cases) were in the R7 group by re-MDACC scores, and after treatment, 50.0% (9 cases) were transferred to the <7 group. For IPSS score low-risk MDS is necessary to perform WPSS score and MDACC score for prognostic analysis, and WPSS score and MDACC score can show the prognostic impact of these drug treatments with decitabine. In patients with low-risk MDS, reduced-dose decitabine has a low incidence of severe hematologic toxicity and early mortality, improves transfusion dependence, enhances the patient's physical status, significantly improves the patient's quality of survival, and may prolong survival. Statistically significant data were not obtained in this study, although in the statistics of the interval from onset to treatment, cytogenetic malignancy, and the relationship between pretreatment WPSS scores and efficacy. Further large series of randomized controlled reduced-dose decitabine for low-risk MDS are necessary to determine which patients are more suitable to benefit from treatment .