OBJECTIVETo study the clinical significance of FMS-like tyrosine kinase 3 (FLT3) mutations including internal tandem duplication (ITD) mutation and point mutation of tyrosine kinase domain (TKD) in children with acute myeloid leukemia (AML).

METHODSBone marrow samples from 116 children with newly-diagnosed AML were obtained. Gene mutations of FLT3/ITD and FLT3/TKD were detected by RT-PCR. The relationship of FLT3 gene mutations with the clinical characteristics and the therapeutic efficacy was observed.

RESULTSFLT3/ITD and FLT3/TKD mutations were detected in 9 cases (7.8%) and 13 cases (11.2%) respectively out of the 116 children. FLT3/ITD mutations were observed in 3 cases of AML-M3 (3/9; 33.3%) and in 3 cases of AML-M5 (3/9; 33.3%). FLT3/TKD mutations were the most common in AML-M3 patients (10/13; 76.9%). The patients with FLT3/ITD mutations had a significantly higher peripheral WBC count and marrow blast percentage compared with the patients without FLT3/ITD mutations at diagnosis (P<0.01). The 3-year overall survival rate in patients with FLT3/ITD mutations was significantly lower than that in patients without FLT3/ITD mutations (38.9% vs 64.3%; P<0.05).

CONCLUSIONSFLT3/TKD mutations are common in children with AML-M3. The AML children with FLT3/ITD mutations present a high peripheral WBC count and a high marrow blast percentage at diagnosis and have an unfavorable outcome.