Internal tandem duplication of the FLT3 gene confers poor overall survival in patients with acute promyelocytic leukemia treated with all-trans retinoic acid and anthracycline-based chemotherapy: an International Consortium on Acute Promyelocytic Leukemia study.

Activating internal tandem duplication (ITD) mutations in the fms-like tyrosine kinase 3 (FLT3) gene (FLT3-ITD) are associated with poor outcome in acute myeloid leukemia, but their prognostic impact in acute promyelocytic leukemia (APL) remains controversial. Here, we screened for FLT3-ITD mutations in 171 APL patients, treated with all-trans retinoic acid (ATRA) and anthracycline-based chemotherapy. We identified FLT3-ITD mutations in 35 patients (20 %). FLT3-ITD mutations were associated with higher white blood cell counts (P < 0.0001), relapse-risk score (P = 0.0007), higher hemoglobin levels (P = 0.0004), higher frequency of the microgranular morphology (M3v) subtype (P = 0.03), and the short PML/RARA (BCR3) isoform (P < 0.0001). After a median follow-up of 38 months, FLT3-ITD(positive) patients had a lower 3-year overall survival rate (62 %) compared with FLT3-ITD(negative) patients (82 %) (P = 0.006). The prognostic impact of FLT3-ITD on survival was retained in multivariable analysis (hazard ratio: 2.39, 95 % confidence interval [CI] 1.17-4.89; P = 0.017). Nevertheless, complete remission (P = 0.07), disease-free survival (P = 0.24), and the cumulative incidence of relapse (P = 0.94) rates were not significantly different between groups. We can conclude that FLT3-ITD mutations are associated with several hematologic features in APL, in particular with high white blood cell counts. In addition, FLT3-ITD may independently predict a shorter survival in patients with APL treated with ATRA and anthracycline-based chemotherapy.