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What is the DPYD biomarker?

The DPYD gene is present in each of the cells in our body. The gene holds the instructions for making a protein called Dihydropyrimidine dehydrogenase. The normal (wild type) Dihydropyrimidine dehydrogenase protein (also DPD) is an enzyme that breaks down chemotherapy drugs commonly used in colorectal cancer treatment and converts them from toxic to non-toxic molecules so they can be removed from the body.

Patients with a DPYD gene mutation either have 1) less efficient enzyme or, 2) complete loss of the enzyme. Therefore, they cannot metabolize drugs such as 5-Fluorouracil (5FU) and similar fluoropyrimidine-based chemotherapies (FOLFOX, FOLFIRI, FOLFIRINOX, and capecitabine). Patients with less-efficient enzyme activity (intermediate metabolizer) who are treated with 5FU or similar drugs may experience severe side effects like neutropenia, diarrhea, and mucositis. Patients with no enzyme activity at all (poor metabolizer) may experience life-threatening fluorouracil toxicity.

What does a DPYD mutation mean?

Experts know about more than 50 different mutations in the DPYD gene. About 5-18% of colorectal cancer patients have mutations in the DPYD gene but only about 1 in 1000 patients have no activity at all.

When and how should I have DPYD biomarker testing?

Testing for DPYD mutations is not required. Patients usually get tested after experiencing severe toxicity during treatment with fluoropyrimidine-based chemotherapy (5-FU or similar drugs such as FOLFOX, FOLFIRI, or FOLFIRINOX, capecitabine). FDA-approved label of these drugs include warning of toxicity.

What do I do with this information?

Every treatment has the potential to cause some side effects. Some people may be more sensitive than others to a particular drug. If you are experiencing severe side effects during treatment with fluoropyrimidine-based chemotherapy (5-FU or similar drugs such as FOLFOX, FOLFIRI, or FOLFIRINOX, Capecitabine), call your doctor immediately. You should also discuss pharmacogenetic testing with your doctor. It may show if you have a mutation in the DPYD gene that puts you at risk for experiencing severe toxicity or side effects.

The Clinical Pharmacogenetics Implementation Consortium (CPIC) recommends lower doses of chemotherapy based on the type of DPYD gene mutations or the level of activity. For patients with complete loss of enzyme activity, fluoropyrimidine-based chemotherapy should be stopped immediately. You should discuss other chemotherapy treatment options with your doctor.

For more on side effects of other chemotherapy regimens, click here.

Download: The DPYD Biomarker

Learn about the DPYD Biomarker.

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