Background
Phase III RCT (COG AALL0434). 1,846 patients with T-cell ALL or T-cell lymphoblastic lymphoma (T-LBL). 2×2 factorial design: randomized to modified BFM (mBFM) vs augmented BFM, and to receive or not receive nelarabine (six courses). Cranial RT (12 Gy) was mandated for CNS-3 disease or T-LBL with initial CNS involvement; omitted in CNS-1/CNS-2. Major question: does nelarabine improve EFS in T-ALL?
Interventions and follow up
Arm A: Augmented BFM chemotherapy × 2.5 years ± nelarabine (6 five-day courses at 650 mg/m²/day)
Arm B: Modified BFM chemotherapy × 2.5 years ± nelarabineCranial RT 12 Gy for CNS+ or T-LBL; omitted for CNS-1/CNS-2 T-ALL
Primary endpoint: DFS
mFollow up: 5.0 year
Arm B: Modified BFM chemotherapy × 2.5 years ± nelarabineCranial RT 12 Gy for CNS+ or T-LBL; omitted for CNS-1/CNS-2 T-ALL
Primary endpoint: DFS
mFollow up: 5.0 year
Results
5-yr DFS (nelarabine): 59.3% vs no nelarabine 51.3%, P=.0165 — significant
5-yr OS (nelarabine): 73.3% vs no nelarabine 65.8%, P=.0174
CNS relapse rate: Low (<5%) regardless of cranial RT in chemotherapy-only patients
T-LBL DFS (nelarabine): No significant benefit in lymphoma stratum
5-yr OS (nelarabine): 73.3% vs no nelarabine 65.8%, P=.0174
CNS relapse rate: Low (<5%) regardless of cranial RT in chemotherapy-only patients
T-LBL DFS (nelarabine): No significant benefit in lymphoma stratum
Adverse events
Main adverse events: Nelarabine: grade ≥3 neurotoxicity 10% (peripheral neuropathy, somnolence, motor weakness). Cranial RT 12 Gy: neurocognitive effects modest vs historical 18–24 Gy; avoided when possible. Augmented BFM: pegaspargase toxicity, thrombosis, pancreatitis.
Conclusions
Nelarabine significantly improved DFS and OS in T-ALL when added to augmented BFM chemotherapy. This established nelarabine-containing augmented BFM as the standard of care for pediatric T-ALL. Low-dose cranial RT (12 Gy) or omission is the contemporary approach for most T-ALL patients.
Key Limitations
Key Limitations: Complex 2×2 factorial design with multiple endpoints. Nelarabine benefit limited to T-ALL, not T-LBL stratum. Long-term neurotoxicity from nelarabine + cranial RT combination requires monitoring. MRD-directed therapy not incorporated in this era of the trial.
Clinical Context
AALL0434 established nelarabine + augmented BFM as standard therapy for pediatric T-ALL. Cranial RT is now used only for CNS-3 disease (12 Gy) or T-LBL with CNS disease; omitted for CNS-1/CNS-2 T-ALL. MRD-directed intensification is the current area of active investigation (AALL1231).
References