Non-A type nucleophosmin 1 gene mutation predicts poor clinical outcome in de novo adult acute myeloid leukemia: differential clinical importance of NPM1 mutation according to subtype.

Mutations of nucleophosmin gene (NPM1) are known to be related to good prognosis in AML patients lacking FLT3 internal tandem duplication (FLT3-ITD). Recently, NPM1 mutations other than type A were reported, but their clinical significance is not well known. Retrospective medical record review of 106 de novo AML patients lacking FLT3-ITD, who received induction chemotherapy from three centers in Korea between 1997 and 2007, was performed. Direct sequencing of NPM1 and RT-PCR for FLT3-ITD was performed on genomic DNA derived from blood samples of patients before induction chemotherapy for detection of mutations. NPM1 mutation was detected in 18 patients, where 13 were type A mutants and 5 were non-type A mutants. CR, CR1-D and OS was not different according to NPM1 mutational status overall. But, non-type A NPM1 mutation was related to shorter CR1-D when compared with NPM1 wild types and NPM1 type A mutation (p = 0.004). OS was shorter in non-type A mutants when compared with NPM1 wild-type patients and NPM1 type A mutants (p = 0.001). The type of mutation of NPM1 is important for prognosis in de novo AML lacking FLT3-ITD. Non-A type NPM1 mutation is a poor prognostic factor.