Researchers at the Spanish National Cancer Research Centre and collaborators developed genomic tests harnessing chromosomal instability (CIN) signatures to predict patient resistance to multiple chemotherapy classes, including platinum compounds, taxanes, and anthracyclines. This advance was validated through retrospective analysis of 840 cancer patients and offers potential to guide personalized therapy decisions, avoid ineffective treatments, and reduce toxicity. The work also aligns with startup Tailor Bio’s efforts to translate CIN biomarkers into clinical testing tools.