Long-term outcomes of haploidentical hematopoietic stem cell transplantation with antithymocyte globulin-based myeloablative conditioning in pediatric refractory or relapsed non-Hodgkin lymphoma.

Importance: The prognosis of pediatric refractory/relapsed non-Hodgkin lymphoma (R/R NHL) remains poor, with limited evidence guiding optimal treatment. Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is a promising strategy for this high-risk population. However, the optimal conditioning regimen and long-term outcomes of haplo-HSCT have not been fully elucidated. Objective: To evaluate the long-term efficacy and safety of antithymocyte globulin (ATG)-based myeloablative haplo-HSCT in pediatric patients with R/R NHL. Methods: Pediatric patients with R/R NHL who underwent ATG-based myeloablative haplo-HSCT at Beijing Children's Hospital between March 2015 and December 2021 were retrospectively enrolled. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method and compared using the log-rank test. Results: A total of 29 pediatric R/R NHL patients were enrolled, including 21 with lymphoblastic lymphoma and 8 with mature T-cell and natural killer-cell lymphoma. The 5-year OS, PFS, cumulative incidence of relapse, and non-relapse mortality were 79.3%, 72.4%, 10.0%, and 17.0%, respectively. At a median follow-up of 5.5 years, the cumulative incidences of Grade III-IV acute graft-versus-host disease (GVHD) and chronic GVHD were 13.8% (4/29) and 44.8% (13/29; predominantly mild), respectively. Thrombotic microangiopathy (TMA) developed in 12 patients and was associated with significantly inferior prognosis ( Interpretation: ATG-based myeloablative haplo-HSCT is a safe and effective treatment for pediatric R/R NHL, offering a viable alternative for patients lacking matched donors or requiring urgent intervention. Early detection and timely treatment of TMA may reduce mortality and improve survival outcomes.