The Clinical and Molecular Characteristics of FLT3 Mutations in Chinese De Novo Adolescent and Adult Acute Lymphoblastic Leukemia Patients

Background Activating mutations in FMS-like tyrosine kinase 3 (FLT3) are frequent in acute myeloid leukemia (AML) and have important prognostic and therapeutic implications. FLT3 aberrations have been detected in a smaller fraction of acute lymphoblastic leukemia (ALL), and their prognostic value is not well established. We therefore assessed the FLT3 mutation in Chinese adolescent and adult ALL patients. Patients and Methods We have examined a cohort of 117 Chinese de novo adolescent and adult ALL patients enrolled between June 2016 and June 2017 from the First Affiliated Hospital of Soochow University. Prognostic factors for the ALL patient population were estimated by the Cox regression method. FLT3 mutation was detected by PCR, and its clinical effect was assessed by Kaplan-Meier curves. Differences in FLT3 mutation rate between subgroups were tested by chi-square test. Results FLT3 mutations accounted for 6.8% (8/117) in our cohort, including 3 internal tandem duplications (2.6%) and 5 tyrosine kinase domains (4.3%, 3 D835Y mutations, 1 M664I mutation, and 1 I867S mutation), which had no clinical significance on either overall survival (OS) or event-free survival. Alterations in FLT3 occurred more often in early thymic precursor (ETP)-ALL compared to non-ETP T-cell acute lymphoblastic leukemia (P = .028). However, the age at onset (P = .004), initial platelet counts (P = .018), and transplantation status (P = .007) were independent prognostic factors of OS for ALL in multivariate analysis. Conclusion The FLT3 mutation was not common in Chinese ALL patients. Age at onset, platelet counts, and transplantation status rather than the presence of the FLT3 mutation were independent prognostic variables for ALL on OS in our cohort. Despite our small sample size, ETP-ALL may indicate a comparable higher FLT3-mutant rate. Because ETP-ALL has been identified as high-risk subgroup, these data warrant clinical studies with the implementation of FLT3 inhibitors in addition to early allogeneic hematopoietic stem-cell transplantation for FLT3-mutant ETP-ALL.