The data from AAML0531, AAML03P1, and CCG-2961 were acquired from the TARGET project, current as of June 30, 2015. The χ² test was used to test the significance of observed differences in patients’ characteristics, and Fisher’s exact test was used when data were sparse. Median differences were compared by the Mann–Whitney or Wilcoxon signed-rank test as appropriate. A P value < .05 was considered statistically significant. The Kaplan–Meier method was used to estimate OS (defined as time from study entry to death) and EFS (time from study entry until failure to achieve CR during induction, relapse, or death). RR was calculated by cumulative incidence methods defined as time from the end of induction I for patients in CR to relapse or death, where deaths without a relapse were considered competing events. Patients who withdrew from therapy due to relapse, persistent central nervous system disease, or refractory disease with >20% BM blasts by the end of induction I were defined as induction I failures. The significance of predictor variables was tested with the log-rank statistic for OS, EFS, and with Gray’s statistic for RR. All estimates are reported with 2× the Greenwood standard errors. Children lost to follow-up were censored at their date of last known contact.

BM, bone marrow; CR, complete remission; EFS, event-free survival; FAB, French-American-British; FLT3, FMS-like tyrosine kinase; ITD, internal tandem duplications; MRD, minimal residual disease; NPM, nucleophosmin; OS, overall survival; RR, relapse risk.