Researchers at the University of Cambridge, Spanish National Cancer Research Centre, and Tailor Bio have developed a genomic test that predicts resistance to chemotherapy in diverse cancer patients by analyzing chromosomal instability (CIN) patterns. By sequencing tumor DNA, the test identifies complex CIN signatures indicative of likely poor response to platinum, taxane, and anthracycline chemotherapy. Validated retrospectively in 840 patients, this tool offers potential to tailor oncology treatments, sparing patients ineffective therapies and associated toxicities, marking a significant advance in precision cancer medicine.