Consensus proposal for revised International Working Group response criteria for higher risk myelodysplastic syndromes

Myelodysplastic syndromes/neoplasms (MDS) are associated with variable clinical presentations and outcomes. The initial response criteria developed by the International Working Group (IWG) in 2000 have been used in clinical practice, clinical trials, regulatory reviews, and drug labels. While the IWG criteria were revised in 2006 and 2018 (the latter focusing on lower-risk disease), limitations persist in their application to higher-risk MDS and in their ability to fully capture clinical benefits of novel investigational drugs or to serve as valid surrogates for longer-term clinical endpoints (e.g., overall survival). Further, issues related to ambiguity and practicality of some criteria lead to variability in interpretation and inter-observer inconsistency in reporting results from the same sets of data. Thus, we convened an international panel of 36 MDS experts and used an established modified Delphi process to develop consensus recommendations for updated response criteria that would be more reflective of patient-centered and clinically relevant outcomes in higher-risk MDS. Among others, the IWG 2023 criteria include changes in the hemoglobin threshold for complete remission (CR), the introduction of CR with limited count recovery (CRL) and CR with partial hematologic recovery (CRh) as provisional response criteria, elimination of marrow CR, and specific recommendations for standardization of time-to-event endpoints and the derivation and reporting of responses. The updated criteria should lead to better correlation between patient-centered outcomes and clinical trial results in an era of multiple emerging new agents with novel mechanisms of action.