Risk Factors for and Impact of Pre-Engraftment Syndrome on Outcomes Following Single-Unit Cord Blood Transplantation...

Pre-engraftment syndrome (PES) is a unique complication of cord blood transplantation (CBT) whose risk factors and impact on transplant outcomes remain controversial. Using a nationwide database in Japan, we analyzed a total of 3734 patients who underwent single-unit CBT. PES occurred in 18.3% of patients, and risk factors for PES included a higher hematopoietic cell transplantation-specific comorbidity index, first transplantation, myeloablative conditioning (MAC), lower total nucleated cell (TNC) dose, and graft-versus-host disease (GVHD) prophylaxis regimens excluding tacrolimus with methotrexate. Patients who developed PES had significantly higher incidences of grade II-IV acute GVHD (53.1% vs. 31.3%, p < 0.001) and chronic GVHD (27.2% vs. 21.7%, p = 0.002) compared to those without PES. Landmark analysis with multivariable adjustment revealed that PES was independently associated with increased non-relapse mortality (NRM, hazard ratio [HR] 1.46; 95% CI 1.22-1.75; p < 0.001), reduced relapse incidence (HR 0.78; 95% CI 0.63-0.96; p = 0.020), and a trend toward inferior overall survival (OS, HR 1.13; 95% CI 0.98-1.30; p = 0.088). Moreover, patients who experienced both PES and acute GVHD had the highest 2-year NRM (31.7%; 95% CI 26.0%-37.6%) and the lowest 2-year OS (55.9%; 95% CI 50.0%-62.4%), compared with those who experienced either PES (NRM 20.7%; OS 65.0%) or acute GVHD (NRM 19.5%; OS 62.8%) (p < 0.001), highlighting the combined effects of these complications. This study, the largest to date on PES, demonstrates its clinical significance as an early complication with lasting effects on transplant outcomes.