A Randomized Phase 3 Trial of Blinatumomab Vs. Chemotherapy As Post-Reinduction Therapy in Low Risk (LR) First Relapse of B -Acute Lymphoblastic Leukemia (B-ALL) in Children and Adolescents/Young Adults (AYAs): A Report from Children's Oncology Group Study AALL1331

Standard treatment of children and AYAs with LR first relapse of B-ALL [LR defined as bone marrow with or without extramedullary (BM±EM) relapse ≥36 months or isolated EM (IEM) relapse ≥18 months from initial diagnosis, and low (<0.1%) BM minimal residual disease (MRD) at the end of reinduction chemotherapy] consists of approximately 2 years of standard chemotherapy without hematopoietic stem cell transplant. The objective of this study was to compare survival [primary: disease-free (DFS); secondary: overall (OS)] of LR first relapse B-ALL patients aged 1-30 years randomized following reinduction chemotherapy (Block 1 of UKALLR3/mitoxantrone arm) to receive either two intensive chemotherapy blocks (Blocks 2 and 3 of UKALLR3) followed by continuation and maintenance chemotherapy of UKALLR3 (chemotherapy control) vs. the same except with integration of three 4-week cycles of blinatumomab, one replacing Block 3 chemotherapy and two added during continuation and maintenance (blinatumomab experimental). All patients with central nervous system (CNS) leukemia at relapse (isolated or combined with BM relapse) received additional intensified CNS-directed chemotherapy (intrathecal and systemic) and 1800 cGy of cranial radiation during maintenance. Patients with testicular leukemia at relapse that persisted after Block 1 reinduction received 2400 cGy testicular radiation during Block 2.