An international collaboration led by the Spanish National Cancer Research Centre and partners at Cambridge and Tailor Bio has developed a novel genomic test leveraging chromosomal instability (CIN) signatures to predict cancer patient resistance to common chemotherapy regimens including platinum, taxane, and anthracycline drugs. By analyzing complex patterns of chromosomal alterations, the assay offers clinicians a tool to personalize treatment and avoid ineffective therapies, potentially improving patient outcomes and reducing exposure to toxic side effects. This was validated retrospectively using genomic data from 840 cancer patients with various tumor types.