International Study for Treatment of Childhood Relapsed Precursor B-Cell ALL 2020 (IntReALL BCP 2020)

Inclusion Criteria: For all study questions: * Confirmed diagnosis of 1st relapsed B-cell precursor ALL * Patients ≥ 1 year and less than 18 years of age at diagnosis of primary ALL and less than 21 years of age at date of inclusion into the study * Patient enrolled in a participating center * Written informed consent (IC) * Start of treatment falling into the study period * No participation in other clinical trials 30 days prior to study enrolment that interfere with this protocol, except trials for primary ALL Specific for SR induction randomization: * Meeting SR criteria * BM involvement (≥ 5% or ≥ 1% leukemic blasts confirmed by 2 quantitative methods) * CD22 positive ALL (\>80% confirmed by flow-cytometry) * No previous history of veno-occlusive disease (VOD)/ sinusoidal obstruction syndrome (SOS) Specific for SR MRD poor response consolidation: * Meeting SR criteria with bone marrow involvement at relapse diagnosis * M1/CR2 and MRD ≥ 10-4 after induction * CD19 positive ALL at relapse (\>10%) Specific for SR MRD good response consolidation: * Meeting SR criteria with bone marrow involvement at relapse diagnosis * M1/CR2 and MRD \< 10-4 after induction * CD19 positive ALL at relapse (\>10%) Specific for HR consolidation arm * Meeting HR or VHR (in case of no possibility to be treated with CAR T cells) criteria * M1/CR2 after induction therapy * CD19 positive ALL at relapse (\>10%) Specific for IEM arm: * Histology or cytology proven extramedullary relapse * No …