Blood 2018 08 11;132(8):815-824. Epub 2018 Jul 11.
Department of Pediatrics, Children's Hospital of Philadelphia and Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA.
Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL; --like ALL) in children with National Cancer Institute (NCI) intermediate- or high-risk (HR) ALL is associated with poor outcome. Ph-like ALL is characterized by genetic alterations that activate cytokine receptor and kinase signaling and may be amenable to treatment with tyrosine kinase inhibitors. The prevalence, outcome, and potential for targeted therapy of Ph-like ALL in standard-risk (SR) ALL is less clear. We retrospectively analyzed a cohort of 1023 SR childhood B-ALL consecutively enrolled in the Children's Oncology Group AALL0331 clinical trial. The Ph-like ALL gene expression profile was identified in 206 patients, and 67 patients with either - (n = 6) or - (n = 61) were excluded from downstream analysis, leaving 139 of 1023 (13.6%) as Ph-like. Targeted reverse transcription polymerase chain reaction assays and RNA-sequencing identified kinase-activating alterations in 38.8% of SR Ph-like cases, including rearrangements (29.5% of Ph-like), -class fusions (1.4%), fusions (1.4%), an fusion (0.7%), and other sequence mutations (, , ; 5.6%). Patients with Ph-like ALL had inferior 7-year event-free survival compared with non-Ph-like ALL (82.4 ± 3.6% vs 90.7 ± 1.0%, = .0022), with no difference in overall survival (93.2 ± 2.4% vs 95.8 ± 0.7%, = .14). These findings illustrate the significant differences in the spectrum of kinase alterations and clinical outcome of Ph-like ALL based on presenting clinical features and establish that genomic alterations potentially targetable with approved kinase inhibitors are less frequent in SR than in HR ALL.