Cells throughout the body carry a gene called DPYD. This gene is responsible for creating an enzyme called dihydropyrimidine dehydrogenase (DPD).
The DPD enzyme works like scissors, it breaks down molecules in the body (uracil and thymine) when they aren’t needed. DPD also breaks down the chemotherapy drug 5-FU.
If there’s a mutation in the DPYD gene, there may not be enough of the DPD enzyme needed to break down the chemotherapy. This is called a DPD deficiency. A DPD deficiency can lead to toxic buildup of chemotherapy and severe side effects. In the most extreme cases, it has led to death.
A blood test can be performed to analyze the DPYD gene and identify the risk of a DPD deficiency. Ideally this is run prior to receiving 5-FU or capecitabine (Xeloda), so that adjustments to the treatment plan can be made if you’re at risk of toxic side effects.
