The advantage of chimeric antigen receptor T cell therapy in pediatric acute lymphoblastic leukemia with E2A-HLF fusion gene positivity: a case series

The E2A-HLF fusion gene is a very poor biomarker in acute lymphoblastic leukemia (ALL) because of its high relapse risk, even with the most intensive chemotherapy and hematopoietic stem cell transplantation (HSCT). Here, we analyzed four cases diagnosed with E2A-HLF fusion gene-positive B-ALL and treated with the CCCG-ALL-2015 protocol based on high-risk stratification from Jun 2017 to May 2020 retrospectively. Three cases (Case 1, 2, 3) were insensitive to conventional therapy and inhibitors with high-level MRD on days 19 and 46, but they all achieved complete remission at the molecular level with Chimeric Antigen Receptor (CAR) T cell therapy regardless of primary resistance or recurrence. Although remission was initially achieved for Case 4, chemotherapeutics was not sensitive after recurrence. However, CAR-T cell therapy gave him the chance to obtain complement remission again. Cytokine release syndrome (CRS) with fever, chills, acute kidney injury, hypotension and capillary leak syndrome and CAR-T related encephalopathy syndrome (CRE) with seizures and encephaledema occurred after CAR-T cell therapy, but symptoms disappeared with effective intensive care. Overall, CAR-T cell therapy enabled the patients to achieve complement remission with controllable adverse events. Our results indicated that CAR-T cell therapy is a feasible and effective therapy for patients with E2A-HLF-positive B-ALL and prompted the authors to report these cases.