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Background: Contemporary risk‐directed treatment has improved the outcome of patients with acute lymphoblastic leukemia (ALL) and TCF3::PBX1 fusion. In this study, the authors seek to identify prognostic factors that can be used to further improve outcome. Methods: The authors studied 384 patients with this genotype treated on Chinese Children's Cancer Group ALL‐2015 protocol between January 1, 2015 and December 31, 2019. All patients provisionally received intensified chemotherapy in the intermediate‐risk arm without prophylactic cranial irradiation; those with high minimal residual disease (MRD) ≥1% at day 46 (end) of remission induction were candidates for hematopoietic cell transplantation. Results: The overall 5‐year event‐free survival was 84.4% (95% confidence interval [CI], 80.6–88.3) and 5‐year overall survival 88.9% (95% CI, 85.5–92.4). Independent factors associated with lower 5‐year event‐free survival were male sex (80.4%, [95% CI, 74.8–86.4] vs. 88.9%, [95% CI, 84.1–93.9] in female, p =.03) and positive day 46 MRD (≥0.01%) (62.1%, [95% CI, 44.2–87.4] vs. 87.1%, [95% CI, 83.4–90.9] in patients with negative MRD, p <.001). The presence of testicular leukemia at diagnosis (n = 10) was associated with particularly dismal 5‐year event‐free survival (33.3% [95% CI, 11.6–96.1] vs. 83.0% [95% CI, 77.5–88.9] in the other 192 male patients, p <.001) and was an independent risk factor (hazard ratio [HR], 5.7; [95% CI, 2.2–14.5], p <.001). Conclusions: These data suggest that the presence of positive MRD after intensive remission induction and testicular leukemia at diagnosis are indicators for new molecular therapeutics or immunotherapy in patients with TCF3::PBX1 ALL. Minimal residual disease ≥0.01% at the end of remission induction was associated with an inferior event‐free survival in patients with TCF3::PBX1 acute lymphoblastic leukemia despite intensified chemotherapy. The presence of overt testicular leukemia conferred a particularly poor outcome. [ABSTRACT FROM AUTHOR]

Summary: The effect of prolonged pulse therapy with vincristine and dexamethasone (VD) during maintenance therapy on the outcome of paediatric patients with TCF3‐PBX1 positive acute lymphoblastic leukaemia (ALL) remains uncertain. We conducted non‐inferiority analysis of 263 newly diagnosed TCF3‐PBX1 positive ALL children who were stratified and randomly assigned (1:1) to receive seven additional VD pulses (the control group) or not (the experimental group) in the CCCG‐ALL‐2015 clinical trial from January 2015 to December 2019 (ChiCTR‐IPR‐14005706). There was no significant difference in baseline characteristics between the two groups. With a median follow‐up of 4.2 years, the 5‐year event‐free survival (EFS) and 5‐year overall survival (OS) in the control group were 90.1% (95% confidence interval [CI] 85.1–95.4) and 94.7% (95% CI, 90.9–98.6) comparable to those in the experimental group 89.2% (95% CI 84.1–94.7) and 95.6% (95% CI 91.8–99.6), respectively. Non‐inferiority was established as a one‐sided 95% upper confidence bound for the difference in probability of 5‐year EFS was 0.003, and that for 5‐year OS was 0.01 by as‐treated analysis. Thus, omission of pulse therapy with VD beyond one year of treatment did not affect the outcome of children with TCF3‐PBX1 positive ALL. [ABSTRACT FROM AUTHOR]

Background: Acute lymphoblastic leukemia (ALL), the most common childhood malignancy, is characterized by recurring structural chromosomal alterations and genetic alterations, whose detection is critical in diagnosis, risk stratification and prognostication. However, the genetic mechanisms that give rise to ALL remain poorly understood.Methods: Using next-generation sequencing (NGS) in matched germline and tumor samples from 140 pediatric Chinese patients with ALL, we landscaped the gene mutations and estimated the mutation frequencies in this disease.Results: Our results showed that the top driver oncogenes having a mutation prevalence over 5% in childhood ALL included KRAS (8.76%), NRAS (6.4%), FLT3 (5.7%) and KMT2D (5.0%). While the most frequently mutated genes were KRAS, NRAS and FLT3 in B cell ALL (B-ALL), the most common mutations were enriched in NOTCH1 (23.1%), FBXW7 (23.1%) and PHF6 (11.5%) in T cell ALL (T-ALL). These mutant genes are involved in key molecular processes, including the Ras pathway, the Notch pathway, epigenetic modification, and cell-cycle regulation. Strikingly, more than 50% of mutations occurred in the high-hyperdiploid (HeH) ALL existed in Ras pathway, especially FLT3 (20%). We also found that the epigenetic regulator gene KMT2D, which is frequently mutated in ALL, may be involved in driving leukemia transformation, as evidenced by an in vitro functional assay.Conclusion: Overall, this study provides further insights into the genetic basis of ALL and shows that Ras mutations are predominant in childhood ALL, especially in the high-hyperdiploid subtype in our research. [ABSTRACT FROM AUTHOR]