The University of Birmingham-led arm of the eSMART trial (Phase I/II, n=66 treated patients across four European countries) reports that high tumor aneuploidy, rather than BRCA-like gene alterations or Ewing sarcoma histology itself, correlated with clinical benefit from low-dose irinotecan plus a PARP inhibitor. Benefit was observed in 12 patients (partial/complete responses or stable disease >6 months). This retrospective biomarker analysis, however, was conducted within a non-randomized, single-arm study whose primary endpoints were safety and tolerability; therefore, the aneuploidy finding remains hypothesis-generating and vulnerable to selection bias. Prior adult oncology data (e.g., the 2022 Nature Reviews Clinical Oncology synthesis by Lord & Ashworth) established that PARP-inhibitor sensitivity tracks with homologous-recombination deficiency, yet pediatric tumors rarely harbor these canonical alterations. The current study therefore highlights a distinct mechanism—genome-wide copy-number instability—potentially widening the therapeutic window for DNA-repair inhibitors in osteosarcoma, neuroblastoma, and medulloblastoma cohorts where cure rates after relapse remain <30%. Notably absent from the MedicalXpress coverage is any discussion of assay standardization: aneuploidy scoring via low-pass whole-genome sequencing can vary by 15-20% across platforms, raising reproducibility concerns for future stratification. A 2023 Journal of Clinical Oncology observational series (n=312 relapsed solid tumors) similarly linked high aneuploidy to improved progression-free survival on ATR/CHK1 inhibitors, suggesting convergent biology that the Birmingham team does not explicitly reference. Conflicts of interest are minimal—CRUK-funded infrastructure with no disclosed industry ties—but the modest sample size (only 12 responders) precludes multivariable adjustment for prior lines of therapy or performance status. If validated in an upcoming randomized expansion cohort, aneuploidy could shift pediatric precision-oncology paradigms from histology-centric to genome-instability-centric trial design.