Oncogenomic profiling in infant-toddler T-ALL identifies NKX2 family genes as drivers linked to favorable outcomes.

T-cell acute lymphoblastic leukemia (T-ALL) is a rare and aggressive hematological malignancy primarily affecting adolescents and young adults and is scarce in infants and toddlers under age 3. Unlike B-ALL, T-ALL in this young population remains poorly characterized due to limited data and lacks evidence-based guidelines to help clinicians determine the optimal treatment approach. In this study, we conducted a comprehensive genetic analysis of infant/toddler T-ALL cases from a French national cohort, utilizing high-throughput targeted sequencing, optical genome mapping, and RNA sequencing. Genetic analysis revealed the absence of dysregulation. Instead, we identified a significant prevalence of rearrangements ( = 9, 33%), co-occurring with alterations ( = 5/9) or chromothripsis-like events ( = 3/9). Additional findings included anomalies (30%), (15%), rearrangements (15%), and rarely, rearrangements (7%). Comparative analyses with 245 patients aged 3-18 years, enrolled in the pediatric FRALLE2000T French protocol, underscored the distinct clinical and genetic profiles of infants/toddlers. Despite presenting with higher rates of hyperleukocytosis and slower responses to treatment, they demonstrated comparable survival outcomes to older pediatric patients, with a 5-year overall survival (OS) rate of 75.4% (95% confidence interval [CI]: 60.0%-94.8%) versus 75.2% (95% CI: 69.8%-81.1%),  = 0.86. Notably, alterations in , , and delineated oncogenic subgroups exhibiting a remarkable 100% OS rate, while patients with or dysregulation experienced less favorable outcomes. This was further supported by analyses of data from the COG AALL0434 trial, enhancing our understanding of T-ALL in infants/toddlers. Large-scale collaborative studies remain essential to confirm these findings and refine treatment strategies.