Donor Lymphocyte Infusion Combined with Azacitidine After Allogeneic HSCT in Pediatric AML: A Single-Center Retrospective Analysis

Ana Maria Bica^1,2Andra Daniela Marcu^1,2Cristina Georgiana Jercan^1,2*Iuliana Iordan^1,2Andreea Serbanica^1,2Irina Avramescu^1,2Matei Colita^2,3Delia Codruta Popa^1,2Ileana Constantinescu^1,2Alexandra Mihaela Ichim¹Andrei Colita^2,3Anca M Colita^1,2

• ¹Fundeni Clinical Institute, Bucharest, Romania
• ²Universitatea de Medicina si Farmacie Carol Davila din Bucuresti, Bucharest, Romania
• ³Spitalul Clinic Coltea, Bucharest, Romania

Donor lymphocyte infusion (DLI) can enhance graft-versus-leukemia (GvL) effects following allogeneic hematopoietic stem cell transplantation (HSCT) in pediatric acute myeloid leukemia (AML). However, the optimal integration of azacitidine (Aza) with DLI in children remains uncertain. We retrospectively reviewed 16 pediatric AML patients (≤18 years) treated at Fundeni Clinical Institute between 2016 and 2024 who received DLI combined with Aza (75 mg/m²/day for 7 days every 4 weeks) post-HSCT. DLI was delivered prophylactically or preemptively—based on mixed donor chimerism (MDC), measurable residual disease (MRD) positivity, or high-risk cytogenetics—or therapeutically for relapse, with or without chemotherapy. Outcomes assessed included overall survival (OS), donor chimerism, relapse rate, and graft-versus-host disease (GVHD). After a median follow-up of 46.5 months, five patients received prophylactic/preemptive DLI and eleven therapeutic DLI (seven with chemotherapy, four without). All prophylactic/preemptive recipients achieved full donor chimerism and MRD negativity, with an OS of 80% at 2.7 years. In the therapeutic group, median OS was 23.8 months for those treated with chemotherapy and 13.8 months without; OS differences between groups were not statistically significant (p = 0.384). Acute GVHD occurred in two patients (12.5%) from the therapeutic + chemotherapy subgroup, while no chronic GVHD or non-relapse mortality occurred. These results indicate that azacitidine combined with DLI is feasible and safe in pediatric AML after HSCT, particularly when used prophylactically or preemptively to restore donor chimerism or eradicate MRD, whereas therapeutic use for overt relapse remains challenging and yields limited benefit. Prospective, multicenter studies are warranted to define optimal timing, dosing, and combination strategies for integrating azacitidine with DLI in this high-risk pediatric population.