OBJECTIVETo analyze the mutation of FLT3 internal tandem duplication (FLT3-ITD) in bone marrow cells from patients with newly-diagnosed acute promyelocytic leukemia (APL).

METHODSThe mutation of FLT3-ITD in bone marrow mononuclear cells (MNCs) from 103 APL patients were screened by polymerase chain reaction (PCR) and the clinical features of ITD positive patients were analyzed.

RESULTSFLT3-ITD mutations were identified in 19.4% (20/103) patients. It was associated with short/variant form of PML-RAR alpha isoforms (P < 0.0001). Among the 20 patients with FLT3-ITD mutation, 16 presented with short, 2 with variant and 2 with long form of PML-RAR alpha isoforms. Patients with FLT3-ITD mutation also presented significantly higher initial peripheral white blood cell count (WBC) (P < 0.01), especially in those with short/variant PML-RAR alpha isoforms (P = 0.015). For patients with long form PML-RAR alpha, there was no significant difference in initial WBC. Out of FLT3-ITD positive patients, 18/20 (90%) obtained complete remission and 16 evaluable patients (2 lost follow-up) remained in first remission in a median follow-up of 26 (11-47) months.

CONCLUSIONFLT3-ITDs are frequently identified in patients with newly diagnosed APL. FLT3-ITD mutation is associated with short/variant form of PML-RAR alpha fusion gene and higher initial WBC. No significant impact on treatment outcome was observed with a limited follow-up.