Fluoropyrimidines (for example, 5-fluorouracil and capecitabine) are medications used to treat different types of cancer. An enzyme in the body called dihydropyrimidine dehydrogenase (or DPD) is needed to break down fluoropyrimidines. If someone does not produce enough of this enzyme, it increases their risk of developing severe toxicity if they are treated with fluoropyrimidines. Severe toxicity means bad reactions that can affect the blood, digestive system, and skin. If someone develops severe toxicity, their cancer treatment may need to be delayed or stopped. Severe toxicity can also lead to hospital admission and, in rare cases, death.

A test called DPYD genotyping aims to identify variants in the DPYD gene, which affects people's production of the DPD enzyme. This test may be able to identify people who are at a higher risk of developing severe toxicity. This allows their treatment plan to be changed before treatment begins, for example, by reducing the fluoropyrimidine dose or choosing an alternative treatment.

This health technology assessment looked at how valid, clinically useful, and cost-effective DPYD genotyping is in people who have planned cancer treatment with fluoropyrimidines. It also looked at how effective a reduced fluoropyrimidine dose is in lowering the risk of severe toxicity, and the budget impact of publicly funding DPYD genotyping. It also considered the experiences, preferences, and values of people who have planned cancer treatment with fluoropyrimidines.