Dihydropyridine 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, such as 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?

Like getting other blood tests done, 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 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 dihydropyridine dehydrogenase gene (DPYD) test?

A DPYD test is a type of pharmacogenomic test. It checks for certain forms of a protein called dihydropyridine dehydrogenase using your genes. Some people have forms of the DPYD gene that puts them at 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 form of the DYPD gene linked to a higher risk of side effects from fluoropyrimidines. It is helpful to know this when creating a treatment plan for now or in the future. You will have this test done once since the genes inherited from your parents rarely change. 

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

This does not mean you cannot receive 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.

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

Does the DPYD test have any limitations?

The test only looks for the most common forms of the DPYD gene. Some people without these forms of the DPYD gene can still be sensitive to the chemotherapy because they have a rare version of the gene this test does not screen for. There are other non-genetic factors, such as 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.