NPM1 but not FLT3-ITD mutations predict early blast cell clearance and CR rate in patients with normal karyotype AML (NK-AML) or high-risk myelodysplastic syndrome (MDS).

Mutations in the NPM1 gene represent the most frequent genetic alterations in patients with acute myeloid leukemia (AML) and are associated with a favorable outcome. In 690 normal karyotype (NK) AML patients the complete remission rates (CRs) and the percentage of patients with adequate in vivo blast cell reduction 1 week after the end of the first induction cycle were significantly higher in NPM1(+) (75% and 80%, respectively) than in NPM1(-) (57% and 57%, respectively) patients, but were unaffected by the FLT3-ITD status. Multivariate analyses revealed the presence of a NPM1 mutation as an independent positive prognostic factor for the achievement of an adequate day-16 blast clearance and a CR. In conclusion, NPM1(+) blast cells show a high in vivo sensitivity toward induction chemotherapy irrespective of the FLT3-ITD mutation status. These findings provide insight into the pathophysiology and help to understand the favorable clinical outcome of patients with NPM1(+) AML.