First name
Jonathan
Middle name
M
Last name
Downie

Title

Association of Combined Focal 22q11.22 Deletion and IKZF1 Alterations With Outcomes in Childhood Acute Lymphoblastic Leukemia.

Year of Publication

2021

Date Published

2021 Aug 19

ISSN Number

2374-2445

Abstract

<p><strong>Importance: </strong>Alterations in the IKZF1 gene drive B-cell acute lymphoblastic leukemia (B-ALL) but are not routinely used to stratify patients by risk because of inconsistent associations with outcomes. We describe a novel deletion in 22q11.22 that was consistently associated with very poor outcomes in patients with B-ALL with IKZF1 alterations.</p>

<p><strong>Objective: </strong>To determine whether focal deletions within the λ variable chain region in chromosome 22q11.22 were associated with patients with B-ALL with IKZF1 alterations with the highest risk of relapse and/or death.</p>

<p><strong>Design, Setting, and Participants: </strong>This cohort study included 1310 primarily high-risk pediatric patients with B-ALL who were taken from 6 independent clinical cohorts, consisting of 3 multicenter cohorts (AALL0232 [2004-2011], P9906 [2000-2003], and patients with Down syndrome who were pooled from national and international studies) and 3 single-institution cohorts (University of Utah [Salt Lake City], Children's Hospital of Philadelphia [Philadelphia, Pennsylvania], and St. Jude Children's Hospital [Memphis, Tennessee]). Data analysis began in 2011 using patients from the older studies first, and data analysis concluded in 2021.</p>

<p><strong>Exposures: </strong>Focal 22q11.22 deletions.</p>

<p><strong>Main Outcomes and Measures: </strong>Event-free and overall survival was investigated. The hypothesis that 22q11.22 deletions stratified the prognostic effect of IKZF1 alterations was formulated while investigating nearby deletions in VRPEB1 in 2 initial cohorts (n = 270). Four additional cohorts were then obtained to further study this association (n = 1040).</p>

<p><strong>Results: </strong>This study of 1310 patients with B-ALL (717 male [56.1%] and 562 female patients [43.9%]) found that focal 22q11.22 deletions are frequent (518 of 1310 [39.5%]) in B-ALL and inconsistent with physiologic V(D)J recombination. A total of 299 of 1310 patients with B-ALL had IKZF1 alterations. Among patients with IKZF1 alterations, more than half shared concomitant focal 22q11.22 deletions (159 of 299 [53.0%]). Patients with combined IKZF1 alterations and 22q11.22 deletions had worse outcomes compared with patients with IKZF1 alterations and wild-type 22q11.22 alleles in every cohort examined (combined cohorts: 5-year event-free survival rates, 43.3% vs 68.5%; hazard ratio [HR], 2.18; 95% CI, 1.54-3.07; P &lt; .001; 5-year overall survival rates, 66.9% vs 83.9%; HR, 2.05; 95% CI, 1.32-3.21; P = .001). While 22q11.22 deletions were not prognostic in patients with wild-type IKZF1 , concomitant 22q11.22 deletions in patients with IKZF1 alterations stratified outcomes across additional risk groups, including patients who met the IKZF1plus criteria, and maintained independent significance in multivariate analysis for event-free survival (HR, 2.05; 95% CI, 1.27-3.29; P = .003) and overall survival (HR, 1.83; 95% CI, 1.01-3.34; P = .05).</p>

<p><strong>Conclusions and Relevance: </strong>This cohort study suggests that 22q11.22 deletions identify patients with B-ALL and IKZF1 alterations who have very poor outcomes and may offer a new genetic biomarker to further refine B-ALL risk stratification and treatment strategies.</p>

DOI

10.1001/jamaoncol.2021.2723

Alternate Title

JAMA Oncol

PMID

34410295

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