The U.S. Food and Drug Administration updated the boxed warning for Genentech’s capecitabine (Xeloda) to explicitly recommend pre‑treatment DPYD genetic testing to identify patients with dihydropyrimidine dehydrogenase (DPD) deficiency, who are at high risk for severe fluoropyrimidine toxicity. The label change elevates testing from a prior 'consider testing' advisory to a recommendation unless immediate treatment is necessary. The move follows patient-advocate pressure and recent workshops with oncologists and reflects growing regulatory momentum toward genotype‑guided dosing for cytotoxic chemotherapies. Clinicians and hospital systems will need to operationalize testing workflows and turnaround times. The label update is likely to accelerate adoption of DPYD assays in oncology clinics and could influence payer coverage and guideline language across cancer societies.