Prevalence and prognostic implications of WT1 mutations in pediatric acute myeloid leukemia (AML): a report from the Children's Oncology Group

Abstract

Recent studies of WT1 mutations in acute myeloid leukemia (AML) mostly report an association with unfavorable clinical outcome. We screened 842 patients treated on 3 consecutive pediatric AML trials for WT1 zinc-finger mutations. Eighty-five mutations were detected in 70 of 842 patients (8.3%). Mutations occurred predominantly in exon 7 (n = 74) but were also found in exons 8 (n = 5) and 9 (n = 6). Normal karyotype was observed in 35.3% of WT1(mut) patients, whereas 27.5% WT1(mut) patients harbored favorable risk cytogenetics. Patients with or without mutations had similar rates of complete remission after one course of induction chemotherapy. Overall survival (OS) for patients with WT1 mutations was 41% versus 54% for those without mutations (P = .016). Corresponding event-free survival (EFS) was also significantly worse for those with WT1 mutations (28% vs 42%; P = .01). However, FLT3/ITD was present in 36% of the WT1(mut) cohort; WT1(mut) patients without FLT3/ITD had similar OS (56% vs 56%, respectively; P = .8) and EFS (35% and 44%, respectively; P = .34) to patients who were wild type for both mutations. In current risk stratification schemes incorporating cytogenetics and FLT3/ITD status, the presence of WT1 mutations has no independent prognostic significance in predicting outcome in pediatric AML. The clinical trials are registered at www.clinicaltrials.gov as #NCT00002798 and #NCT00070174.

Figures

Figure 1

Location of WT1 zinc-finger mutations. Graphical depiction of the 85 mutations detected in 70 of 842 pediatric patients with AML screened. Mutations clustered in the N-terminal portion of exon 7 but were also detected in exons 8 and 9.

Figure 2

Clinical significance of WT1 mutations in pediatric AML. Kaplan-Meier estimates show that patients with WT1 mutations have shorter (A) OS and (B) EFS from study entry than patients without these mutations. (C) Cumulative incidence of relapse was also worse for patients with WT1 mutations.

Figure 3

Outcomes stratified by combined WT1 and FLT3/ITD mutation status. When stratifying patients by combined FLT3/ITD and WT1 status, patients with both mutations had the worst (A) OS, (B) EFS, and (C) RR. Of the 2 mutations, FLT3/ITD imparts a stronger negative effective on survival outcome.