Case Report: Clinical response to TKI therapy in T-cell acute lymphoblastic leukemia with rare ABL1 rearrangement.

BACKGROUND: T-cell acute lymphoblastic leukemia (T-ALL) with ABL1 rearrangement is an extremely rare disease, and its clinical significance has not been precisely defined. We report the clinical characteristics of a pediatric patient with T-cell acute lymphoblastic leukemia harboring ABL1 rearrangement and the treatment response to tyrosine kinase inhibitor (TKI) therapy, providing a reference for clinical management with this subtype. CASE REPORTS: A 3-year-old boy with T-ALL and ZBTB16::ABL1 fusion (RNA-seq) showed poor response to induction chemotherapy, failing remission at D33. Dasatinib (75 mg/m2/day) was added concurrently with CAM chemotherapy. At D90, morphological CR and flow-MRD negativity were achieved, though qPCR remained positive at 0.08%. Isolated CNS relapse occurred during Block III consolidation. Subsequent management included autologous CD7 CAR T-cell therapy and allogeneic HSCT; post-transplant evaluation confirmed sustained leukemia remission. However, the patient developed HHV-6 encephalitis and adenovirus hepatitis with hepatic failure; life-sustaining support was withdrawn at the family's request. The patient was discharged and lost to follow-up. CONCLUSION: This paper presents the second reported case to date of TKI treatment for T-cell acute lymphoblastic leukemia harboring the ZBTB16::ABL1 fusion. Following a review of the relevant literature on ABL1-rearranged T-ALL, we conclude that the accumulation of additional cases is essential to better characterize this rare molecular subtype and to guide evidence-based treatment decisions.