Dihydropyrimidine Dehydrogenase Gene (DPYD) Test

What is pharmacogenomics?

Pharmacogenomics, also called pharmacogenetics, is the study of how your genes affect your body’s response to medicines. The word pharmacogenomics is made up of the words pharmacology and genomics. Pharmacology is the study of the uses and effects of medicines. Genomics is knowing what genes are and how they work. Genes carry genetic information that you inherit (get) from your parents. Genes determine things about you, like your eye color or blood type. Your genes can also influence how your body will react to some medications.

What is pharmacogenomic testing?

Pharmacogenomic testing is when your genes are studied to find out if a medicine is right for you. It can help see how your body may respond to one or more medications. But it cannot tell you how you will respond to all medications.

A pharmacogenomic test can help figure out:

• If you could have serious side effects from medicines.
• If a medicine will work for you.
• The best dose of a medicine.

How is it done?

Pharmacogenomic testing is often done as a blood test. A small amount of blood will be removed from a vein through a needle placed through your skin. The blood goes from the needle into a container like a tube. The blood is sent to a lab, and it will take about 7-10 days for the results. Your provider will talk to you about your results, and they will be part of your medical records. After the test is done, your blood sample will be thrown out and not used anymore.

What is a dihydropyrimidine dehydrogenase gene (DPYD) test?

A DPYD test is a type of pharmacogenomic test. It checks for certain kinds of protein called dihydropyrimidine dehydrogenase using your genes. Some people have the kind of DPYD gene that puts them at a higher risk for side effects from fluoropyrimidine chemotherapy compared to others. Fluoropyrimidine chemotherapies include 5-fluorouracil injection (Adrucil®, 5-FU) and capecitabine pills (Xeloda®).

This test will be ordered if your provider wants to know if you have the kind of DYPD gene linked to a higher risk of side effects from fluoropyrimidines. It is helpful to know this when creating your treatment plan. You will have this test done once since the genes inherited from your parents rarely change. 

What if I have a kind of the DPYD gene linked to a higher risk of side effects?

This does not mean you cannot get fluoropyrimidine medications. Your provider will use the test results to decide which chemotherapy is best to treat your cancer. Your provider may choose to lower the dose of the fluoropyrimidine chemotherapy, or your provider may treat your cancer with other chemotherapy medications.

If you do have a kind of the DPYD gene, it is important to share this information with family members. Biological parents, brothers, sisters, and children may have the same kind of the DPYD gene. If you are finding it hard to share this information with your family, you can talk to your provider about helpful resources.

Does the DPYD test have any limitations?

The test only looks for the most common kinds of the DPYD gene. Some people without these kinds of the DPYD gene can still be sensitive to the chemotherapy because they have a rare version of the gene that this test does not screen for. There are other non-genetic factors, like age, that may also increase your risk of side effects. No matter your results, your provider will closely watch how you are responding to chemotherapy.

Will insurance pay for the DPYD test?

Healthcare insurance companies have different types of coverage policies. Many policies cover genetic tests that are used to guide medical management. It is always best to talk to someone from your insurance company to help figure out if this testing is covered.