IL7R expression is associated with CNS disease and CNS relapse in pediatric BCP-ALL patients. Correlation analysis of IL7R expression in 61 E2A-PBX1⁺ pediatric patients with white blood cell (WBC) count (A) and CNS status (B). Unpaired Student t test, 2-sided P value. (C) Correlation analysis of IL7R expression in 98 pediatric BCP-ALL patients of mixed cytogenetics and CNS status. Further definitions are provided in supplemental Table 1. Unpaired Student t test, 2-sided P value. (D) IL7R expression in ALL cells retrieved from the CSF of 8 children with CNS relapse of BCP-ALL as well as from the bone marrow (BM) of 22 patients at diagnosis, and cells from the BM of 20 patients at the time of isolated BM relapse (data set, van der Velden et al¹⁶ ). Unpaired Student t test, 2-sided P value. (E) Kaplan-Meier survival curve showing reduced isolated CNS (iCNS) relapse-free probability in children with upregulated IL7R gene expression in diagnostic BM (n = 131) or peripheral blood (n = 76) samples of children with high-risk ALL. IL7R upregulation was defined as a z score for gene expression ≥1.2 (TARGET phase 1 data set). AU, arbitrary unit; IL7R, interleukin 7 receptor.