Background: Post-hoc analysis of COG P9904 identified a low risk (LR) group of SR B-ALL patients aged 1-9.99 years with WBC < 50,000/µL, no CNS3, and either ETV6/RUNX1 or double trisomies (DT) of chromosomes 4 and 10 with day 8 peripheral blood (PB) and day 29 marrow (BM) minimal residual disease (MRD) < 0.01% who had a 5-year event-free survival (EFS) of 97±2% and overall survival (OS) 98.8±0.8%. Outstanding results were also obtained for LR patients on COG AALL0331 using CCG-based ALL therapy. AALL0932 tested prospectively whether LR B-ALL patients could attain a 5-year EFS ≥95% with these regimens. Methods: Following a 3-drug induction, eligible AALL0932 LR patients had NCI SR B-ALL (no testicular leukemia, unfavorable genetics or Down syndrome) with DT or ETV6/RUNX1 fusion, CNS1, no steroid pre-treatment, with Day 8 PB and Day 29 BM MRD < 0.01%. Between 2010-16, 603 LR patients were randomized to P9904-based regimen LR-M (n = 301) or CCG 1991/COG AALL0331-based regimen LR-C (n = 302). LR-M included 6 24-hour infusions of 1 gm/m² of methotrexate (MTX) with leucovorin rescue, but no anthracyclines or alkylating agents. Maintenance followed with daily 6-mercaptopurine (6-MP) and weekly oral MTX, and every 16 week 7-day pulses of dexamethasone (DEX) with vincristine (VCR) on days 1 and 8. Boys and girls were treated for 2.5 years from diagnosis. LR-C had no 24-hour MTX infusions, but included 2 Interim Maintenance (IM) phases with VCR and escalating IV MTX without leucovorin rescue given every 10 days for 5 doses, flanking an 8-week Delayed Intensification (DI) phase that included DEX, VCR, pegasparagase, doxorubicin (75 mg/m²), cyclophosphamide (1 gm/m²) and 8 doses of low-dose cytarabine (75 mg/m2/dose). LR-C Maintenance included daily 6-MP and weekly oral MTX with 5-day pulses of DEX and 1 dose of VCR given every 12 weeks. Girls received 2 years and boys 3 years of therapy from the start of IM I. Results: Both regimens achieved outstanding outcomes: 5-yr disease-free survival (±SE) 98.8%±0.8% for LR-M and 98.5%±0.9% for LR-C (p = 0.67). Both had 5-yr OS 100%. Therapies were well tolerated with higher rates of mucositis (12.9 vs 6.3%; p = 0.008) and allergic reactions (2.3% vs 0%; p = 0.02) on LR-C. Conclusions: AALL0932 demonstrated that application of stringent risk criteria can identify a favorable B-ALL subgroup almost certain to be cured with either LR-M or LR-C, allowing physicians and families to select the optimal treatment approach in the future. Clinical trial information: NCT01190930

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