Prognostic Implication of FLT3 and N-RAS Gene Mutations in Acute Myeloid Leukemia

Internal tandem duplication of the FLT3 gene and point mutations of the N-RAS gene are the most frequent somatic mutations causing aberrant signal-transduction in acute myeloid leukemia (AML). However, their prognostic importance is unclear. In this study, their prognostic significance was analyzed in 201 newly diagnosed patients with de novo AML except acute promyelocytic leukemia. Three patients had mutations in both genes, 43 had only theFLT3 gene mutation, 25 had only the N-RAS gene mutation, and 130 had neither. These mutations seemed to occur independently. Both mutations were related to high peripheral white blood cell counts, and the FLT3 gene mutation was infrequently observed in the French-American-British (FAB)-M2 type. AML cases with wild FLT3/mutant N-RAS had a lower complete remission (CR) rate than those with wild FLT3/wild N-RAS, whereas the presence of mutant FLT3 did not affect the CR rate. Univariate analysis showed that unfavorable prognostic factors for overall survival were age 60 years or older (P = .0002), cytogenetic data (P = .002), FAB types other than M2 (P = .002), leukocytosis over 100 ± 109/L (P = .003), and the FLT3 gene mutation (P = .004). However, the N-RAS gene mutation was only a marginal prognostic factor (P = .06). For the subjects under 60 years old, multivariate analysis showed that theFLT3 gene mutation was the strongest prognostic factor (P = .008) for overall survival. The FLT3 gene mutation, whose presence is detectable only by genomic polymerase chain reaction amplification and gel electrophoresis, might serve as an important molecular marker to predict the prognosis of patients with AML.