Response assessments in low-risk and high-risk myelodysplastic syndromes (MDS).

The myelodysplastic syndromes (MDS) are a heterogeneous group of hematopoietic disorders that differ with regard to etiology, pathologic and clinical features, treatment, and outcomes. MDS are chronic, progressive diseases that may be broadly categorized into early phase ("low-risk") and late-phase ("high-risk") groups based on prognostic criteria and the differential pathologic and cytogenetic features that drive the MDS phenotype in these disease phases. Consequently, the goals for treatment and management options also differ for low-risk MDS compared with high-risk MDS. Alleviation of disease-related complications, including transfusion requirements, and hematologic improvement are key treatment goals in low-risk MDS. In contrast, altering the natural history of disease, including improvements in overall survival and progression-free survival, are the most important treatment goals in high-risk MDS. To address the heterogeneity of MDS in patient populations enrolled in clinical trials and to resolve problems resulting from variability in the quality and quantity of responses to treatment, the International Working Group has developed standardized response criteria for MDS that are relevant for both low-risk and high-risk categories. The application of the standardized International Working Group response criteria in clinical trials is enabling the comparison of results from various clinical trials in MDS. Furthermore, the International Working Group response criteria provide an important framework for clinical development of new treatments options that may be particularly appropriate for specific MDS subsets.