Background
Phase 3, multicenter, pseudo-factorial (2×2) randomized trial (COG AALL0434). N=1,562 evaluable, age 1–31 years, newly diagnosed T-cell ALL (T-ALL) or T-cell lymphoblastic lymphoma (T-LBL). Two independent randomized questions in the Augmented BFM (ABFM) backbone: (1) methotrexate schedule — C-MTX (Capizzi-escalating MTX + PEG-asparaginase) vs HD-MTX (5 g/m² ×4 with leucovorin); and (2) in intermediate/high-risk patients — nelarabine 650 mg/m²/day ×5d (six 5-day courses in ABFM consolidation) vs no nelarabine. Published JCO 2020.
Interventions and follow up
Arm A: Augmented BFM + HD-MTX + nelarabine (6 cycles, N=176)
Arm B: Augmented BFM + HD-MTX, no nelarabine (N=185)
Primary endpoint: 4-year disease-free survival (DFS)
mFollow up: ~6 years
Arm B: Augmented BFM + HD-MTX, no nelarabine (N=185)
Primary endpoint: 4-year disease-free survival (DFS)
mFollow up: ~6 years
Results
4-year DFS (nelarabine vs no nelarabine, HD-MTX arm — primary): 86.2±3.2% vs 78.0±3.7%, P=.024
4-year DFS (nelarabine vs no nelarabine, C-MTX arm): No significant benefit — interaction with MTX schedule
4-year OS (HD-MTX + nelarabine): ~92% vs ~87% (no nelarabine)
T-LBL outcomes: 4-year EFS ~85%, OS ~91% across arms — comparable to T-ALL with ABFM backbone
4-year DFS (nelarabine vs no nelarabine, C-MTX arm): No significant benefit — interaction with MTX schedule
4-year OS (HD-MTX + nelarabine): ~92% vs ~87% (no nelarabine)
T-LBL outcomes: 4-year EFS ~85%, OS ~91% across arms — comparable to T-ALL with ABFM backbone
Adverse events
Nelarabine toxicity: peripheral neuropathy (any grade ~10%; grade ≥3 ~2%); CNS toxicity (somnolence, confusion); lymphopenia
Backbone toxicity: asparaginase-related pancreatitis and allergy common across arms; osteonecrosis with dexamethasone-containing backbone
Overall: no unexpected increase in infections with nelarabine; grade ≥3 AEs similar with vs without nelarabine when used with HD-MTX
Backbone toxicity: asparaginase-related pancreatitis and allergy common across arms; osteonecrosis with dexamethasone-containing backbone
Overall: no unexpected increase in infections with nelarabine; grade ≥3 AEs similar with vs without nelarabine when used with HD-MTX
Conclusions
Adding nelarabine to the Augmented BFM backbone with HD-MTX significantly improved 4-year DFS (86% vs 78%) in pediatric/young adult T-ALL without increased toxicity. Nelarabine incorporation is now standard of care for frontline T-ALL in children and young adults in the US and Europe.
Key Limitations
Nelarabine benefited only the HD-MTX cohort — the interaction with C-MTX raises questions about mechanism and generalizability. Pseudo-factorial design means the randomizations were not fully statistically independent. Nelarabine benefit in T-LBL was not separately randomized. Long-term late-neurotoxicity (peripheral neuropathy) data are limited, as is mature OS beyond ~6 years. Conducted 2007–2014, pre-MRD-guided nelarabine dosing.
Clinical Context
AALL0434 established nelarabine + Augmented BFM (with HD-MTX) as the standard frontline regimen for pediatric/young adult T-ALL in the US, replacing prior non-nelarabine regimens. FDA approved nelarabine for R/R T-ALL in 2005; AALL0434 confirmed its frontline role. Subsequent COG protocols (AALL1231, AALL1732) incorporate nelarabine + HD-MTX routinely; ESMO recognizes nelarabine in the T-ALL armamentarium.