A collaborative study led by the Spanish National Cancer Research Centre and the University of Cambridge has developed genomic biomarkers based on chromosomal instability (CIN) signatures to predict patient resistance to chemotherapies such as platinum agents, taxanes, and anthracyclines across multiple cancers. By sequencing tumor DNA from 840 patients, the test identifies distinct CIN patterns indicative of reduced treatment efficacy, potentially sparing patients from ineffective and toxic chemotherapy. This innovation could facilitate personalized treatment strategies, optimizing therapeutic benefit and reducing healthcare costs associated with unresponsive regimens.