Contrasting impacts of pretransplant cytoreduction and post-transplant maintenance on outcomes of allogeneic haematopoietic stem cell transplantation in myelodysplastic syndromes: Real-world multicentre evidence.

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) remains the only curative therapy for patients with high-risk myelodysplastic syndrome (MDS). However, the optimal timing and value of pretransplant cytoreduction and post-transplant maintenance remain unclear, and transplant-modifiable variables are not well defined in real-world settings. We retrospectively analysed 215 consecutive MDS patients who underwent allo-HSCT. Clinical, molecular and transplant-related factors were evaluated for their impact on relapse, relapse-free survival (RFS) and overall survival (OS). TP53 mutation, complex karyotype, and positive measurable residual disease (MRD) after cytoreductive treatment were associated with increased relapse risk. Among transplant-related variables, younger donor age (<42 years) and higher CD34+ cell dose (≥3.1 × 106/kg) significantly reduced relapse risk. Notably, pretransplant cytoreduction did not confer measurable benefit on outcomes. In contrast, post-transplant maintenance therapy significantly reduced relapse incidence and prolonged RFS. Pretransplant cytoreduction offers limited clinical value, whereas post-transplant maintenance and modifiable transplant variables (CD34+ cell dose and donor age) substantially improve outcomes after allo-HSCT for MDS. These findings highlight actionable strategies that may refine transplant decision-making and optimize outcomes in clinical practice.