Defining remission and relapse after allogeneic hematopoietic cell transplantation in myelodysplastic/myeloproliferative neoplasms and optimization of transplantation outcomes: Recommendations from the EBMT practice harmonisation and guidelines committee.

Myelodysplastic/myeloproliferative neoplasms (excluding CMML) are rare and heterogenous malignancies with recurrent and overlapping clinicopathological abnormalities. Classification and characterization continue to evolve, but outcomes remain unsatisfactory and allo-HCT is currently the only curative therapy. Experience with these diseases is limited by rarity, accounting for <1% of allo-HCT procedures in Europe annually. Transplant indications have recently been described by this group, however response assessment, post-transplant surveillance and management of poor graft function, splenomegaly and relapse are not well established. To address this gap, the European Society for Blood and Marrow Transplantation (EBMT) Practice Harmonization & Guidelines (PH&G) Committee and the Chronic Malignancies Working Party (CMWP) collaborated to develop a practical and expert consensus-based guideline. Criteria for remission confirmation are proposed, including timing/thresholds for morphological, molecular, cytogenetic and chimerism analysis, aiming to harmonize comparisons in registry data and between international series. Suggestions for managing poor graft function and splenomegaly are designed to broadly align with those for myelofibrosis and related disorders. Relapse post-transplant remains a frequent challenge and the lack of robust evidence, in both the pre-transplant/post-transplant setting, underpins a need for collaborative clinical trials. This document serves as a framework to model post-transplant care, guide future research and address unresolved questions.