Allogeneic Hematopoietic Stem Cell Transplantation for Children With Mixed Phenotype Acute Leukemia: A Single-Center Retrospective Study.

[PURPOSE] Mixed phenotype acute leukemia (MPAL) represents an uncommon but heterogenous disease, often posing both a diagnostic and therapeutic challenge. The purpose of this retrospective study was to analyze the overall survival, event-free survival, and severity of associated complications after allo-HSCT in children with MPAL, and provide feasible recommendations for the treatment of MPAL patients.

[PATIENTS AND METHODS] We retrospectively analyzed a total of 14 pediatric patients with MPAL who received allo-HSCT at our center between January 2010 and June 2024.

[RESULTS] In terms of immunophenotype, coexpression of myeloid and B-lymphoid antigens was observed in 10 patients (71.4%), and myeloid and T-lymphoid antigens in 4 (28.6%). Chromosomal abnormalities were found in 8 patients (57.1%) and BCR/ABL(+) was the most common fusion gene (3/14; 21.4%). All 14 patients underwent allo-HSCT after achieving the CR1 (78.6% with MRD-negative status pretransplantation). Among the 14 transplanted children, the OS rate was 92.9% and the EFS rate was 85.7%. No significant difference in OS, EFS, and CIR rates between children with Haplo-HSCT and those with MSD-HSCT (P>0.05). The rate of acute GVHD was 57.1% (8/14), and the rate of chronic GVHD was 71.4%, of which 90% were assessed as mild cGVHD, with the skin being the most common organ involved in cGVHD. Only one patient developed TA-TMA and died from transplant-related complications.

[CONCLUSION] The children with MPAL who received allo-HSCT after MRD-negative CR often had a favorable disease control. Compared with patients receiving conventional chemotherapy, pediatric patients who received allo-HSCT showed a significant improvement in OS, EFS, and CIR rates. Although the incidence of cGVHD was relatively high, most of them were assessed as mild with no significant impact on daily activities.