Effect of FMS-Like Tyrosine Kinase-3 Mutations on Prognosis in Acute Myeloid Leukemia: A Single Institution Experience between 2000 and 2007.

Mutations of the FMS-like tyrosine kinase-3 gene (FLT3), including internal tandem duplication (ITD) of the juxtamembrane domain or activating point mutations of the second tyrosine kinase domain involving codon 835 or 836 are among the most common molecular abnormalities in acute myeloid leukemia (AML). A clear negative impact of FLT3 mutation on survival has been demonstrated in AML patients younger than 60 years; however, this negative effect on prognosis or survival has not been confirmed in older patients. We evaluated 661 patients with AML treated at MD Anderson Cancer center between 2000 and 2007 for FLT3 mutations including 281 patients ≤ 60 years and 380 patients > 60 years. Median age for the entire group was 65 years (range, 17 to 86). A FLT3 mutation was present in 124 patients (18.7%). Patients with FLT3 mutations had a significantly higher WBC (median, 16.5 vs. 4.2, p<0.001) and a higher percentage of bone marrow blasts (median, 62% V/S 40%, p<0.001) at initial presentation. These differences were equally seen in both sexes. Patients with FLT3 mutations were younger than those without mutations (median age 58 vs. 64, p=0.005). Patients with FLT3 mutations were less likely to have an antecedent hematological disease compared to those without mutations (p<0.001). FLT3 mutations were less frequent in patients with core binding factor leukemia [t(8;21), inv(16)]. FLT3 mutations were more common in patients with acute promyelocytic leukemia (APL) than other FAB subgroups (p<0.001). Induction death and complete remission rates were not affected by FLT3 status. When favorable prognosis subgroups [APL, t(8;21), inv(16)] were excluded, patients with FLT3 mutations had a significantly shorter overall survival; this difference was seen in patients younger than 60 (p=0.019), as well as in patients over 60 (p=0.015). We have further confirmed a clear negative impact of FLT3 mutations on survival in patients ≤ 60 years and have demonstrated a negative impact on survival even in patients older than 60 years. FLT3 inhibitors should be considered as a component of therapy in older patients with non-favorable AML and FLT3 mutation.