IKZF1 deletion is an independent predictor of outcome in pediatric acute lymphoblastic leukemia treated according to the ALL-BFM 2000 protocol

Abstract

IKZF1 gene deletions have been associated with a poor outcome in pediatric precursor B-cell acute lymphoblastic leukemia. To assess the prognostic relevance of IKZF1 deletions for patients treated on Berlin-Frankfurt-Münster Study Group trial ALL-BFM 2000, we screened 694 diagnostic acute lymphoblastic leukemia samples by Multiplex Ligation-dependent Probe Amplification. Patients whose leukemic cells bore IKZF1 deletions had a lower 5-year event-free survival (0.69±0.05 vs. 0.85±0.01; P<0.0001) compared to those without, mainly due to a higher cumulative incidence of relapses (0.21±0.04 vs. 0.10±0.01; P=0.001). Although IKZF1 deletions were significantly associated with the P2RY8-CRLF2 rearrangement, their prognostic value was found to be independent from this association. Thus, IKZF1 deletion is an independent predictor of treatment outcome and a strong candidate marker for integration in future treatment stratification strategies on ALL-BFM protocols. Clinicaltrials.gov identifier: NCT00430118.

Figure 1.

Treatment outcome of patients with pediatric ALL comparing patients with and without IKZF1 deletions. Kaplan-Meier estimates for the whole cohort of 694 patients: (A) event-free survival (EFS) at 5 years, (B) cumulative incidence of relapse (CIR) at 5 years, and (C) overall survival (OS) at 5 years. For the intermediate risk group: (D) EFS, (E) CIR, and (F) OS.