The FDA revised the boxed warning for Genentech’s Xeloda (capecitabine) to explicitly recommend testing patients for DPYD gene variants prior to initiating therapy, unless immediate treatment is required. The agency now warns that patients with complete DPD deficiency face serious adverse reactions or death and advises avoiding Xeloda in patients with homozygous or compound heterozygous DPYD variants that cause complete enzyme deficiency. The labeling change follows advocacy and new evidence discussed at an FDA‑AACR workshop earlier this year and aligns with updated clinical guidelines advising pre‑treatment risk assessment. The revision is expected to influence oncology prescribing practice and could accelerate adoption of preemptive pharmacogenetic screening to reduce severe fluoropyrimidine toxicities.