Impact of TCF3 Rearrangement on CNS Relapse in Egyptian Pediatric Acute Lymphoblastic Leukemia

Background: TCF3 rearrangement mostly t(1;19) (q23;p13)/TCF3-PBX1 gene is associated with favorable outcome in acute lymphoblastic leukemia (ALL) upon treatment with intensification protocols; however, it is associated with higher incidence of central nervous system (CNS) relapse which may affect outcome of patients. Objectives: We aimed to assess TCF3 rearrangement in newly diagnosed pediatric ALL patients in relation to clinical and laboratory parameters, CNS relapse, and clinical outcome. Patients and Methods: Eighty newly diagnosed pediatric ALL patients following at Pediatric Hematology Oncology Clinic, Ain Shams University Hospitals were included in this study. Their ages ranged from 0.75 to 16 years. Seventy six (95%) patients had B-lineage ALL and four (5%) had T-lineage ALL. Data recorded included;age, sex, extramedullary manifestations, CNS, and testes infiltrations, risk stratification, response to treatment, and CBC and BM findings. TCF3 rearrangement was assessed by FISH technique using dual color break-apart probe. Results: TCF3 rearrangement [t(1;19) (q23;p13)] was detected in 16 (20%) out of the 80 studied patients, and it was significantly associated with splenomegaly, lymphadenopathy, CNS infiltration at presentation, high total leucocytic count, low platelet count, high-risk group, and isolated CNS relapse. These results identify a group of high-risk ALL patients with high incidence of CNS relapse and poor response to standard therapeutic regimen. Conclusion: Analysis of TCF3 rearrangement [t(1;19) (q23; p13)] at diagnosis may provide a valuable target for modified and intensified CNS-directed chemotherapeutic protocol aiming to improve the patients' outcome.