Minimal residual disease at end of induction and consolidation remain important prognostic indicators for newly diagnosed children and young adults with very high-risk (VHR) B-lymphoblastic leukemia (B-ALL): Children’s Oncology Group AALL1131.
Authors: Salzer Wanda L. , Burke Michael James , Devidas Meenakshi , Dai Yunfeng , Heerema Nyla A. , Carroll Andrew J. , Gore Lia , Hilden Joanne M. , Larsen Eric , Raetz Elizabeth A. , Winick Naomi J. , Carroll William L. , Hunger Stephen , Loh Mignon L. , Wood Brent L. , Borowitz Michael J. 
Published: June 2021

10004 Background: Children and young adults with very high risk (VHR) B-acute lymphoblastic leukemia (B-ALL) [13-30 years of age with any features or 1-30 years of age with adverse prognostic features including KMT2A rearrangements, iAMP21, hypodiploidy (<44 chromosomes/DNA index < 0.81), central nervous system disease, end of induction (EOI) minimal residual disease (MRD) >0.01%, or induction failure] collectively have a predicted 4-year disease free survival (DFS) of approximately 70%. Whether patients with VHR B-ALL who are MRD positive at EOI and become MRD negative at the end of consolidation (EOC) will have improved survival versus patients remaining MRD positive at EOC is unknown. Methods: Patients with newly diagnosed NCI high risk B-ALL enrolled on AALL1131 or NCI standard risk B-ALL enrolled on AALL0932 and classified as VHR at EOI were treated on the VHR stratum of AALL1131 which sought to improve DFS with intensive post-Induction therapy using fractionated cyclophosphamide (CPM), etoposide (ETOP) and clofarabine (CLOF).Patients were randomly assigned post-Induction to Control Arm (CA) with modified augmented BFM CPM + fractionated cytarabine + mercaptopurine, Experimental Arm 1 (Exp1) with CPM + ETOP, or Experimental Arm 2 (Exp2) with CLOF + CPM + ETOP during Part 2 of Consolidation and Delayed Intensification. Doses of vincristine and pegaspargase were identical on all arms. Exp2 was permanently closed September 2014 due to excessive toxicities, and these patients are excluded from this report. MRD was measured by 6-color flow cytometry at EOI and for those who consented at the EOC. Results: 4-yr DFS for all patients (n=823) with VHR B-ALL was 76.8 ± 2.0%. As we reported previously, 4-year DFS was not significantly different between CA and Exp 1 (85.5 ± 6.8% versus 72.3 ± 6.3%; p=0.76; Burke, Haematologica 2019). 4-yr DFS for patients who were EOI MRD <0.01%, (n=325) versus >0.01 (n=498) was 83.3% ± 2.6% vs 72.0% ± 2.8%, p=0.0013. 4-Year DFS of Patients EOI MRD > 0.01%. Conclusions: MRD is a powerful prognostic indicator in VHR B-ALL with inferior outcomes in patients who are EOI MRD positive. Among patients who were EOI MRD positive treated on Exp1, outcomes were similar for EOC MRD negative and EOC MRD positive, though numbers were small. In contrast, patients who were EOI MRD positive treated on CA that were EOC MRD negative had significantly improved DFS compared to those that were EOC MRD positive. The CA remains the standard of care for COG ALL trials. With this therapy, patients with VHR B-ALL that are EOI MRD positive and EOC MRD negative have significantly improved DFS compared to those that remain MRD positive at EOC. Clinical trial information: NCT02883049. [Table: see text]