Probability of EFS. (A) Five-year probability of EFS in relation to FLT3/ITD. Children with FLT3/ITD-positive AML (n = 27) have significantly poorer 5-year pEFS (46%; [SE, 4%]) when compared with children without this particular mutation (n = 207; pEFS, 29% [SE, 9%]; P = .0046, log-rank test). (B) Two-year probability of EFS related to the mutant/WT-FLT3 ratio. Patients with FLT3/ITD mutations were divided into 2 groups according to the mutant/WT-FLT3 ratio. Children with ratios lower than or equal to the median (0.69) have outcomes similar to those of FLT3/ITD-negative patients (P = .26), whereas patients with ratios greater than the median have significantly worse outcomes than ITD-negative patients (P = .037). The difference between patients with ratios lower than or equal to the median versus those with high ratios was not significant (P = .41), but numbers were small.