Data were retrieved from 118 children and AYA diagnosed with r/r B-ALL treated with CAR T-cell therapy: tisagenlecleucel (n = 108, 92%) or tandem CD19/CD22 CAR T-cell therapy (n = 10, 8%), in five Spanish tertiary centers between January 2019 and April 2024. Here, CD19 is linked to acute lymphoblastic leukemia.