Analysis of the therapeutic effect of allogeneic hematopoietic stem cell transplantation in the treatment of pediatric acute lymphoblastic leukemia with fusion gene: a case series.

[BACKGROUND] The fusion gene () is present in <1% of B-cell acute lymphoblastic leukemia (ALL) patients, mainly in older children and adolescents. Patients with fusion B-ALL consistently have dismal outcomes, even after hematopoietic stem cell transplantation (HSCT). Chimeric antigen receptor T-cell (CAR-T) therapy and donor lymphocyte infusion (DLI) applied in this kind of disease have rarely been reported. In this case series, we will focus on the safety and effectiveness of CAR-T and DLI treatments. This may refine therapeutic strategies and improve survival for this high-risk subgroup.

[CASE DESCRIPTION] In this case series, we review the clinical course of 4 pediatric patients with fusion B-ALL. All four patients treated with Chinese Children Leukemia Group (CCLG)-2018-ALL protocol based on high-risk stratification. Two patients (case 1 and case 4) maintained non-remission after intensive therapy and then accepted CD19-CAR-T therapy. All four patients achieved complete remission before HSCT and were negative for minimal residual disease and fusion in the bone marrow. One patient (case 3) succumbed to complication of HSCT. Two patients (case 1 and case 4) who accepted DLI treatment after HSCT were still alive. One patient (case 2) relapsed after HSCT. Although accepting CAR-T and DLI treatments after HSCT, she died due to primary disease recurrent relapse.

[CONCLUSIONS] The combination of CAR-T-cell therapy before HSCT and pro-DLI treatment after HSCT may represent an effective strategy to improve outcomes in these pediatric patients.