Decitabine has shown clinical benefits in patients with intermediate (INT)-2 or high-risk myelodysplastic syndrome (MDS), determined according to the International Prognostic Scoring System (IPSS), but the benefits have not been well demonstrated in patients with lower-risk (IPSS low or INT-1) disease. Recently, it was proposed that the prognosis for patients with IPSS lower-risk disease is heterogeneous, with a substantial proportion of these patients having poor survival.This study included patients with IPSS lower-risk MDS from the DRAMA (An Observational Study for Dacogen Long-Term Treatment in Patients With Myelodysplastic Syndrome; NCT01400633) and DIVA (A Study for Dacogen Treatment in Patients With Myelodysplastic Syndrome; NCT01041846) studies, which were prospective observational studies on the efficacy and safety of decitabine treatment in patients with MDS. Using the Lower-Risk Prognostic Scoring System [LR-PSS], we classified IPSS lower-risk MDS. Patients in each LR-PSS category were divided according to overall response (OR) to decitabine treatment, and survival outcomes were compared.One hundred sixteen patients were enrolled: LR-PSS category 1 (n = 12; 10.3%), category 2 (n = 56; 48.3%), and category 3 (n = 48; 41.4%). Survival outcomes differed among the 3 categories (P = .046). The overall survival according to OR showed a significant difference in total patients (P = .008) and category 3 patients (P = .003). We analyzed predictive factors for OR, but no variable was found to significantly affect OR.Decitabine treatment showed a survival benefit in the higher-risk group of IPSS lower-risk MDS patients who responded to treatment, and classification using the LR-PSS category was helpful for this subgroup, indicating that decitabine treatment might alter the natural course of disease in these patients.