Characteristics of FLT3 gene mutation and clinical efficacy of tyrosine kinase inhibitor in patients with mixed phenotype acute leukemia / 白血病·淋巴瘤

ABSTRACT

Objective:To analyze the incidence and mutation characteristics of FLT3 gene mutation and clinical efficacy of tyrosine kinase inhibitor (TKI) in patients with mixed phenotype acute leukemia (MPAL).Methods:A total of 48 patients with MPAL who were admitted to Hebei Yanda Lu Daopei Hospital from June 2015 to February 2018 were retrospectively analyzed. The common mutated 58 genes in hematologic malignancies were detected by using amplicon-targeted next generation sequencing, of which internal tandem duplication (ITD) and point mutation occurred in the hotspot region of exon 14, 15 and 20 in FLT3 gene. Multiplex polymerase chain reaction (PCR) analysis was used to detect 35 gene fusions in hematological neoplams.Results:There were 7 cases of FLT3 mutation in 48 MPAL patients, which were all ITD mutations. The median length of the inserts of FLT3-ITD was 48 bp, and one MPAL patient carried 2 multiple length inserts simultaneously, and the median variant allele frequency (VAF) was 40.5% (7.9%-84.7%). There were no statistically significant differences in clinical and genetic characteristics between FLT3 mutation-positive and FLT3 mutation-negative MPAL patients (both P > 0.05). Among 7 FLT3 mutation-positive MPAL patients, 4 cases were often accompanied with RUNX1 mutation. A total of 4 MPAL patients with FLT3-ITD-positive received sorafenib or sunitinib combined chemotherapy, and 3 of them achieved complete remission. Conclusions:ITD mutation is the main part in the FLT3 mutation of MPAL patients. FLT3-ITD-positive MPAL patients are often accompanied with RUNX1 mutation, which may benefit from targeted therapy with FLT3 kinase inhibitor.