Allogeneic Hematopoietic Stem Cell Transplantation for Infant Leukemia: A Single-Center Case Series and Narrative Review

Background/Objectives: Acute leukemias (AL) in children under 1-year-old are combined under the term “infant leukemia” and are a very rare malignancies, accounting for up to 5% of all childhood AL cases. The predominance of unfavorable clinical and laboratory characteristics leads to unsatisfactory treatment results, even with the use of modern treatment protocols. Patients/Methods: A comprehensive search through MEDLINE, PubMed, Scopus, and ScienceDirect using infant leukemia-related keywords was performed and included a final set of 52 academic articles. Our own experience included 11 patients with infant leukemia underwent allo-HSCT (allogeneic hematopoietic stem cell transplantation) at the NN Blokhin National Medical Research Center of Oncology in 2021–2023. Types of leukemia included acute myeloid leukemia, lymphoblastic leukemia, and mixed-phenotype acute leukemia. The most frequent cytogenetic aberration was KMT2A. All patients were in clinical and hematological remission, but four had positive MRD status (minimal residual disease). Donors: haploidentical—5 (45.4%), matched unrelated donor—5 (45.4%), and matched related donor—1 (9.2%). Graft manipulations: post-transplant cyclophosphamide was given to three patients with haplo-HSCT, and TCRαβ/CD19 depletion was performed in two patients. The type of immunosuppressive therapy (IST) varied based on the donor. Conditioning regimens were myeloablative. Results: Median follow-up was 23.5 months. Acute GVHD grade I–II developed in two patients (18%) and grade III–IV in three patients (27%). The overall survival rate was 54.5% (n = 6). The relapse rate after allo-HSCT was 18% (n = 2). The most common cause of treatment failure was infectious complications in the early post-transplant period (70%). Conclusions: Our center’s experience demonstrated acceptable transplant-related mortality and satisfactory relapse rates after allo-HSCT in patients with infant leukemia. The treatment of acute leukemia in infants is challenging, and optimal protocols are being developed around the world specifically for these patients. Taking into account the characteristics of this age group, the choice of chemotherapy drug doses should be carefully considered, and the indications for allo-HSCT should be balanced.