TP53 mutations define a high-risk subgroup in pediatric Acute Myeloid Leukemia with distinct molecular and cytogenetic features Free

Background Despite advances in risk-adapted therapy, outcomes in relapsed/refractory pediatric AML remains poor. TP53 mutations are established as high-risk in adult AML, yet their prognostic and therapeutic relevance in pediatric AML is unclear and not integrated into current risk models and treatment guidelines. Given the unique clonal dynamics and the lack of clinical data, there is a critical unmet need for pediatric-specific analyses of pathogenic TP53 mutations to improve prognosis and treatment in pediatric AML.

Methods We analyzed 486 de-novo pediatric AML patients (0.1–18 years) who were diagnosed between January 2015 and June 2022 and enrolled in the AML-BFM-2012/2017 registries in Germany. Patients with Down syndrome, secondary or treatment-related AML, myelosarcoma, or acute promyelocytic leukemia (APL) were excluded. Diagnostic mutational profiling was performed using targeted next-generation sequencing with the TruSight™ Myeloid panel (Illumina), covering 54 AML-associated genes. Clinical, cytogenetic, and molecular data were correlated with TP53 mutation status. Survival outcomes were assessed using the Kaplan–Meier method, log-rank test, and Cox proportional hazards regression.

Results We identified 18 pathogenic TP53 mutations in 15 (3.1%) pediatric AML patients: 9 frameshift, 6 missense, and 3 nonsense mutations. Eight patients harbored TP53 mutations with high variant allele frequency (~50%) and located in known pathogenic hotspots or truncating regions, suggestive of potential germline origin. Notably, one patient harbored the same TP53 mutation at initial diagnosis and relapse, indicating clonal persistence of a dominant mutant clone. TP53 mutations were associated with significantly worse overall survival (OS, 53±13% vs. 79±2%, p=0.001)and event-free survival (EFS, 40±13% vs. 59±2%, p=0.01). Complete remission (CR) was achieved in 11 (73%) pediatrics with TP53 mutations, while three experienced early death (ED). Among 12 TP53-mutated patients (excluding three with ED), five patients underwent hematopoietic stem-cell transplantation (HSCT) in 1^st CR leading to improved survival rates (OS, 80±18% vs. 57±19% ; EFS, 80±18% vs. 29±17%). When stratified by risk groups according to the AML-BFM recommendations, TP53-mutated patients showed worse survival, which was even slightly inferior to high-risk stratified patients (OS, 53±13% vs. 62±4% and EFS, 40±13% vs. 47±4%). After adjustment for multiple covariates, TP53-mutation remained an independent predictor of poor survival (HR 2.9, p=0.01). TP53-mutant cases were strongly associated with complex karyotypes (47% vs. 18%, p=0.01), with a trend towards monosomic karyotypes (20 vs. 7%, p=0.05) and increased frequency of trisomy 8 (33% vs. 14%, p=0.05). Notably, none of these cases harbored core-binding factor (CBF) mutations (0 vs. 18%). The co-mutational molecular genetic landscape showed enrichment of additional molecular alterations compared to the wild-type cohort (mean 2.9 vs. 1.2, p=0.001) characterized by fewer abnormalities in genes associated with activated signaling (i.e, NRAS 7% vs. 21%, p=0.1) and more frequent alterations in epigenetic regulatory genes (i.e, ASXL1 20% vs. 5.5%, p=0.02, KDM6A 13% vs. 1%, p<0.001 ). These specific molecular and cytogenetic patterns likely reflect an underlying biologically distinct leukemic profile associated with TP53 mutations in pediatric AML.

Conclusion This large-scale analysis comprehensively characterizes TP53 mutation as a biologically and clinically high-risk subgroup in pediatric AML. The distinct molecular and cytogenetic patterns observed suggest a unique leukemic profile. These findings strongly support incorporating pathogenic TP53 mutations into future risk stratification models in pediatric AML. Early HSCT in first remission may improve outcomes, highlighting the need for tailored treatment strategies in this high-risk population in pediatric AML.