BackgroundRefinement of risk-based treatment stratification by minimal residual disease (MRD) at different time points has improved outcomes of childhood acute lymphoblastic leukemia (ALL). In this prospective study we evaluated effects of such stratification, including intensification of therapy based on response assessment at day-15 and MRD at day-29 of induction to test if treatment intensification would improve outcomes.Methods241 patients, 1–14 years old, newly diagnosed with ALL, were recruited and stratified by risk and MRD response into three treatment Arms (A, B, or C). Arm A was modified from COG AALL0331, B from AALL0232, and C from AALL0232 and AALL0434. Assignments were according to NCI risk, phenotype, rapid vs. slow early response (SER), steroid pretreatment, MLL rearrangement (MLLR), CNS3, and testicular involvement. Patients on Arm A had treatment intensified early based on day-15 marrow results or late based on end-of-induction MRD.Results5-year OS, EFS, and CIR were 89.5% ± 4.0%, 87.6% ± 4.3%, and 7.1% ± 3.5%. No significant difference was found by B- vs. T cell phenotype. 5-year OS, EFS, and CIR for B-cell ALL were 90.5% ± 2.4%, 88.7% ± 2.6%, and 6.4% ± 2.0%. Outcomes for patients with t(1;19)/TCF3-PBX1 and MLLR were significantly (p ≤ 0.05) worse than for other patients. MRD level at end-of-induction associated with outcomes, but association with a specific MRD value at end-of-induction varied significantly by NCI-risk group. Late treatment intensification based on end-of-induction MRD significantly improved survival outcomes for NCI-SR patients, however, patients with NCI-HR and positive MRD at end-of-induction had significantly inferior outcomes despite intensification. MRD transitions between day-15 and day-29 of induction associated with differences for OS and EFS.ConclusionsArm switching to a more intensive protocol had mixed results. Assigning patients by end-of-induction MRD-risk alone did not reflect response kinetics of the different NCI-risk groups. Although late treatment intensification improved outcomes of NCI-SR patients with positive MRD at end-of-induction, further refinement is needed to improve outcomes of NCI-HR with SER. Integration of NCI-risk group with specific MRD value and time point allows more refined treatment stratification.Trial Registration Protocols were approved by King Abdullah International Medical Research Center and Ethics Review Committee RC08053J

Background The outcome of children with acute lymphoblastic leukemia (ALL) in developing countries is less favorable than in developed countries, primarily due to resource constraints. However, it is unknown whether the therapeutic results differ. Thus, we hypothesized that outcomes in resource‐rich developing countries would be similar to those in industrialized regions. Procedure We performed a retrospective analysis of 224 consecutive children with ALL, who were treated according to the Children's Cancer Group (CCG) protocols between January 2001 and December 2007. High‐risk (HR) and standard‐risk (SR) patients were treated with modified CCG‐1961 and CCG‐1991 protocols, respectively. Modifications included substitution of dexamethasone for prednisone in HR patients and addition of two intrathecal methotrexate treatments for CNS2 patients during induction. All patients received double delayed intensification with two interim maintenance phases. Results Five‐year overall survival (OS), event‐free survival (EFS) and disease‐free survival (DFS) were 84.7 ± 2.4%, 77.0 ± 2.9%, and 81.4 ± 2.7%, respectively. Remission was achieved in 98.1% of the patients. Induction failure and relapse rates were 1.9% and 15.1%, respectively. Death as the first event occurred in 6.4% of cases, of which 2.7% and 3.7% involved deaths in induction and remission, respectively. Interestingly, a significant reduction in induction deaths was observed over time. Conclusions Despite the encouraging results observed in the present study, our patients displayed significantly lower survival outcomes compared to subjects treated in major clinical trials conducted by leading leukemia cooperative groups. Furthermore, this work underscores the need for targeted interventions to reduce death as the first event in developing regions. Pediatr Blood Cancer 2015;62:945–950. © 2014 Wiley Periodicals, Inc.