At the end of induction, patients who were judged to be standard-risk average were then randomized in a 2x2 design to either standard or intensified consolidation, and to standard interim maintenance with delayed intensification, or to intensified interim maintenance with delayed intensification.
The intensified interim maintenance with delayed intensification randomization was closed in 2008 because of superior results with escalating intravenous methotrexate during interim maintenance for standard-risk ALL patients treated in the CCG 1991 trial. Subsequently, all patients enrolled in AALL0331 received escalating intravenous methotrexate during interim maintenance.
Also in AALL0331, patients with Down syndrome who had standard-high ALL were given intensified consolidation and a single vs. double intensified interim maintenance with delayed intensification; patients without Down syndrome and standard risk high received the double intensified interim maintenance regimen.
Standard-risk low Down syndrome patients and non–Down syndrome patients participated in a randomization to additional pegaspargase doses during consolidation and interim maintenance.