AbstractWe report long-term results of treatment of myelodysplastic syndrome (MDS) with erythropoietin and granulocyte colony-stimulating factor (G-CSF). A total of 129 patients were followed up 45 months after last inclusion in the Nordic MDS Group studies. Erythroid response rate was 39% and median response duration 23 months (range, 3-116 months or more). Complete responders showed longer response duration than partial responders (29 versus 12 months, P = .006). The International Prognostic Scoring System (IPSS) groups Low/Intermediate-1 (Low/Int-1) had longer response duration than Int-2/High (25 versus 7 months, P = .002). The time until 25% developed acute myeloid leukemia (AML) was longer in the good and intermediate predictive groups for erythroid response compared with the poor predictive group (52 versus 13 months, P = .008). Only 1 of 20 long-term responders developed AML. We assessed the effect on long-term outcome by comparing treated patients with untreated patients selected from the IPSS database using multivariate Cox regression, adjusting for major prognostic variables. There was no difference in survival (odds ratio [OR], 0.9; 95% confidence interval [CI], 0.7-1.2; P = .55) or risk of AML evolution (OR, 1.3; 95% CI, 0.7-2.2; P = .40) between treated and untreated patients. Patients with high/intermediate probability of response and with IPSS Low/Int-1 show frequent and durable responses without adverse effects on outcome, while other patients should not be considered candidates for this treatment.