Donor lymphocyte infusion for prophylaxis and treatment of relapse in pediatric hematologic malignancies after allogeneic hematopoietic stem cell transplant

Background: Donor lymphocyte infusion (DLI) is effective for managing patients with hematologic malignancies after allogeneic hematopoietic stem cell transplant (HSCT). However, few studies have explored its optimal use in pediatric populations. Herein, we report our single-center experiences of DLI and factors for predicting its outcomes. Methods: This retrospective study included pediatric patients who had received DLI (between June 1998 and December 2022) after allogeneic HSCT. Data regarding patient characteristics, preemptive DLI disease status, and DLI characteristics were collected. The primary outcomes were overall survival (OS), event-free survival (EFS), and graft-vs-host-disease (GVHD) development. Results: The study cohort comprised 17 patients with acute leukemia, 3 with chronic leukemia, and 3 with lymphoma. Prophylactic, preemptive, and therapeutic DLI were used in seven, seven, and nine patients, respectively. Patients' median age and DLI dose were 9 years and 4.6 × 10⁷ CD3⁺ cells/kg, respectively. The 5-year OS, EFS, and nonrelapse mortality were 43.5%, 38.3%, and 13.3%, respectively. Approximately 39% of the patients developed grade III or IV acute GVHD, whereas moderate/severe chronic GVHD (cGVHD) occurred in 30% of the evaluable patients. Patients' disease status before HSCT (p = 0.009) and DLI (p = 0.018) were the key factors influencing EFS. The implementation of a dose escalation schedule was associated with a marginal reduction in the risk of moderate/severe cGVHD (p = 0.051). A DLI dose of ≥5 × 10⁷ CD3⁺ cells/kg was significantly associated with a high moderate to severe cGVHD risk (p = 0.002) and reduced OS (p = 0.089). Conclusion: Patients' disease status before HSCT and DLI may help predict EFS. The use of DLI as a prophylactic and preemptive modality leads to a favorable 5-year EFS. To safely deliver DLI in children, clinicians must maintain vigilant monitoring and prepare patients in advance when escalating the dose to ≥5 × 10⁷ CD3⁺ cells/kg.