EASIX score predicts non‐relapse mortality and severe infection in elderly patients undergoing allo‐HSCT

Summary Allogeneic haematopoietic stem cell transplantation (allo‐HSCT) is increasingly used in older patients, but non‐relapse mortality (NRM) remains a major concern. The Endothelial Activation and Stress Index (EASIX) has shown prognostic value for transplant outcomes, yet its utility in elderly patients remains unexplored. This study included 164 patients aged ≥60 years undergoing haploidentical HSCT across 12 centres in China (2016–2023). Serial EASIX scores were calculated at eight timepoints throughout the peri‐transplant period. Longitudinal log2‐EASIX patterns were analysed using group‐based trajectory modelling (GBTM). The results indicated that elevated pretransplant log2‐EASIX (log2‐EASIX‐PRE) significantly correlated with inferior overall survival (OS: HR = 1.25, 95% CI 1.07–1.47, p = 0.005), increased NRM (HR = 1.32, 95% CI 1.08–1.62, p = 0.007) and higher incidence of severe infections (HR = 3.73, 95% CI 1.77–7.89, p < 0.001). The optimal EASIX‐PRE cut‐off was 4.25, with patients exceeding this threshold showing worse 2‐year outcomes (OS: 24.3% vs. 59.3%, p < 0.001; NRM: 54.3% vs. 24.5%, p = 0.001). GBTM revealed two distinct trajectory patterns: patients in the log2‐EASIX Spiking group experienced significantly higher NRM compared to the log2‐EASIX Smooth group (HR = 4.58, 95% CI 1.72–12.2, p = 0.002). These findings establish pretransplant EASIX as a clinically actionable biomarker in elderly allo‐HSCT recipients, with dynamic monitoring enabling early risk stratification for personalised interventions.