Allogeneic Hematopoietic Stem Cell Transplantation in Infant Leukemia: Vague Prospects? (Series Cases and Brief 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 the 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) in NN Blokhin National Medical Research Center of Oncology in 2021-2023. Types of leukemia included acute myeloid leukemia, lymphoblastic leuke-mia, and mixed-phenotype acute leukemia. The most frequent cytogenetic aberration was KMT2A. All patients were in first complete remission. Donors: haploidentical – 5 (45.4%), matched related donor – 1 (9.2%), matched unrelated donor – 5 (45.4%). Graft manipulations: post-transplant cyclophosphamide was given to 2 patients with hap-lo-HSCT, and TCRαβ/CD19 depletion was performed in 3 patients. The type of immu-nosuppressive 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 2 patients (18%), and grade III–IV in 3 patients (27%). The current survival rate is 64% (n=7). The relapse rate after allo-HSCT was 9%. The most common cause of treatment failure was infectious complications in the early post-transplant period. Con-clusions: 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 care-fully considered and the indications for allo-HSCT should be balanced.