Impact of FLT3ITD mutation level on outcome according to NPM1. (A) OS in patients with NPM1 mutation (N = 329) compared with NPM1 wild-type (n = 319). (B) RFS in patients with NPM1 mutation (N = 242) compared to NPM1 wild-type (n = 183). The significant impact of FLT3ITD mutation level on outcome was evident in NPM1-mutated AML. In NPM1-mutated AML, the effect of the FLT3ITD mRNA level displayed a dose-dependency. Thus, patients with a FLT3ITD level ≥ 0.50 showed the worst OS and RFS compared to patients with a FLT3ITD level between 0.01 and 0.49 and patients without a FLT3ITD. Differences between the score groups were highly significant (P ≤ .001).