# Efficacy and Safety of Donor Lymphocyte Infusion After Allogeneic Hematopoietic Stem Cell Transplantation in Pediatric Patients

## TL;DR

This study shows that donor lymphocyte infusions after stem cell transplants in children can safely prevent cancer relapse and graft rejection.

## Contribution

The study introduces a gradual dosing strategy for donor lymphocyte infusions in children, achieving high efficacy with low graft-versus-host disease.

## Key findings

- 83% of MRD-positive patients remained relapse-free with preemptive DLI.
- 82% of patients with genetic diseases and mixed chimerism responded to preemptive DLI.
- Prophylactic DLI achieved 100% success without relapse or GVHD.

## Abstract

This retrospective study evaluates the efficacy and safety of donor lymphocyte infusion (DLI) after allogeneic hematopoietic stem cell transplantation (HSCT) in children. We describe the long‐term use of preemptive, prophylactic, and therapeutic DLI with a gradual dose increase in half‐log increments. Under close monitoring, we increased the DLI dose only in patients that did not show signs of graft‐versus‐host disease (GVHD). In the preemptive cohort, 10 of 12 patients (83%) with minimal residual disease (MRD) positivity remained relapse‐free. Among 11 patients with genetic diseases and mixed chimerism, nine (82%) responded to preemptive DLI. Six patients (100%) of the prophylactic cohort with a very high risk of relapse had a successful outcome without relapse or GVHD. Three of the five patients (60%) of the therapeutic cohort were successfully treated with DLI. We observed acute GVHD (grade I and II) in only two patients (6%). The results of our study indicate that the long‐term use of DLI is a promising strategy and can effectively prevent relapse, graft rejection, and even cure relapse. The observed low rate of GVHD may be attributed to the gradual dose increase. Therefore, we consider DLI a safe and effective therapeutic option.