Prognostic significance of early nk cell recovery in pediatric t-cell replete allogeneic hematopoietic stem cell transplantation.

Early immune reconstitution, particularly of natural killer (NK) cells with strong graft-versus-leukemia effects, is crucial for the prognosis of patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). This retrospective study examined 122 pediatric patients with acute lymphoblastic leukemia (ALL) or acute myeloid leukemia (AML) who underwent T-cell replete allo-HSCT at the Children's Hospital of Soochow University from 2019 to 2021. Peripheral blood lymphocyte counts on days 30 and 60 post-transplant were analyzed, focusing on NK cell recovery and its impact on overall survival (OS), relapse-free survival (RFS), non-relapse mortality (NRM), relapse, graft-versus-host disease, and CMV reactivation. Patients were categorized into high and low NK cell groups by the median NK cell counts at day 30 (NK30) and day 60 (NK60) after HSCT. Patients with high NK30 and NK60 levels had significantly better 3-year OS rates compared to their respective low NK count groups (86.8% ± 4.7% versus 67.6% ± 7.0%, P = 0.046; 95.7% ± 3.0% versus 63.7% ± 8.7%, P < 0.001, respectively). NK60 was found to be an independent predictor for 3-year OS and RFS in multivariate analysis. Early NK reconstitution was also related to lower NRM rates. However, this correlation disappeared in patients with ALL and those undergoing haploidentical transplantation. In addition, A positive association between early T cell and NK cell reconstitution was found in our study. Higher NK cell counts on days 60 can predict superior OS, RFS and lower NRM in pediatric AML allo-HSCT patients.