Results in pediatric T-ALL patients treated in trial AIEOP-BFM ALL 2009: Prognostic factors in the context of modern risk-adapted therapy

To improve the outcome of pediatric T-cell acute lymphoblastic leukemia (T-ALL) patients, the AIEOP-BFM ALL 2009 trial modified T-ALL stratification and treatment based on AIEOP-BFM ALL 2000 and other pediatric ALL groups' results. This report aims to describe the outcome of T-ALL patients in trial AIEOP-BFM ALL 2009 and evaluate prognostic features defined within the end of induction (EOI) therapy, for future protocols stratification and interventions. From 06/2010 to 02/2017, 872 T-ALL patients, aged 1–17, were enrolled. High risk (HR) criteria were prednisone poor response (PPR), Day 15 flow cytometry minimal residual disease (MRD) ≥ 10%, no complete remission at EOI, or polymerase chain reaction (PCR)-MRD ≥ 5 × 10⁻⁴ at end of consolidation (EOC). Three Cox regression models on event-free survival (EFS) evaluated prognostic factors. Overall, 5-year EFS and survival were 79.9% ± 1.4% and 84.9% ± 1.2% with cumulative incidence of relapse (CIR) and death of 13.0% ± 1.2% and 5.9% ± 0.8%. Five-year EFS and CIR were 86.8% ± 1.6% and 8.7% ± 1.3% in non-HR patients (n = 470); 71.9% ± 2.3% and 18.0% ± 1.9% in HR patients (n = 402). High PCR-MRD levels at EOI and EOC were prognostic in all models, with EOC-MRD ≥ 5 × 10⁻³ related to a hazard ratio of 6.22 (P < 0.001). When a model considered factors identified at EOI only, central nervous system (CNS)3 (hazard ratio = 2.3, P < 0.001), PPR (hazard ratio = 1.74, P = 0.02), and high EOI-MRD (hazard ratio 4.71 for ≥5 × 10⁻² vs. negative, P < 0.001) significantly impacted EFS. Results of T-ALL patients in AIEOP-BFM ALL 2009 were favorable. While EOC-MRD remained the strongest prognostic predictor, PPR, CNS3 disease, and EOI-MRD showed relevant prognostic value, with CNS3 and EOI-MRD ≥ 5 × 10⁻² being candidate criteria for early stratification and intervention modifications.