5-fluoracil (5-FU) is a chemotherapy agent belonging to the fluoropyrimidine family, often used to treat a range of cancers including: colorectal, head and neck, breast, pancreatic and stomach cancer. 5-FU is metabolized by the dihydropyrimidine dehydrogenase enzyme (DPD) which is encoded by the DPYD gene.
Several variants within the DPYD gene have been described that lead to decreased DPD activity, or complete loss of function. Patients with these variants are at an increased risk of severe or fatal 5-FU toxicity. Therefore, implementation of DPD deficiency screening by genotyping will allow a more accurate prediction of toxicity and chemotherapeutic response, enabling the appropriate treatment to be offered to patients.