Fluoropyrimidine-Associated Toxicity in Two Gastrointestinal Cancer Patients: Potential Role of Common DPYD Polymorphisms.

While the majority of patients can be treated safely with fluoropyrimidine, some experience severe fluoropyrimidine-associated toxicity. The frequency and severity of these adverse events vary from patient to patient and are partially explained by genetic polymorphism into the dihydropyrimidine dehydrogenase (DPYD) gene. Carriers of the rare allelic variants DPYD*2A, DPYD*13, and DPYD D949V are more likely to experience severe adverse reactions during fluoropyrimidine-based therapy. However, these 3 genetic variants explain only a small percentage of the overall drug toxicity, and more frequent ones such as homozygous or compound heterozygous DPYD V732I can play a key role.