What Is — DPD Deficiency?

5-fluorouracil (5-FU) and capecitabine are the main ones, along with tegafur-based regimens. These all belong to a drug family called fluoropyrimidines, and they all rely on DPD to be cleared from the body. If your oncologist mentions any of these drugs by name, DPD is the relevant enzyme to ask about. Your oncologist will tell you which drug applies to your specific regimen.

In a person with undetected DPD deficiency, standard-dose fluoropyrimidine treatment can cause severe damage to the gut lining, a deep fall in white blood cells, and effects on the nervous system. This can appear after the first or second treatment cycle and progress quickly. It does not look like typical chemotherapy side effects — it tends to be more severe and earlier in onset. The degree of risk depends on how much enzyme activity is reduced.

There are two approaches. One looks at the DPYD gene in a blood sample to identify known variants associated with reduced enzyme activity. The other measures DPD enzyme activity in the blood directly. Both require a blood sample. Neither test is universally available across all centres in India. Ask your oncologist which type is accessible to you and whether it can be arranged before your first treatment.

Not as a universal requirement. In parts of Europe, the EMA required DPD testing before fluoropyrimidine treatment from 2020. In India, CDSCO had not mandated it as of the date this page was written, and availability depends on where you are being treated. Asking your oncologist directly is the most reliable way to find out what is available in your case. The question is always worth asking.

Not automatically. The presence of a DPYD variant does not by itself determine whether you can or cannot receive the drug. Your oncologist interprets the result alongside your cancer type, the treatment being considered, and your overall health. Testing gives your treating team information they can factor into their planning. What that means for your specific result and situation is a conversation for your oncologist, not something a web page can answer.

ESMO and CPIC have both published guidance supporting DPD testing before fluoropyrimidine chemotherapy. Whether testing is offered in your case, and what is available at your centre, depends on your treating team and their resources. The guidance supports offering the test, but your oncologist makes the decision for your specific circumstances. Asking about it at your next appointment is a reasonable step.

DPD activity is determined largely by the DPYD gene, which is inherited. If you carry a significant DPYD variant, your biological relatives have a higher chance of carrying the same variant than the general population. Whether those relatives need testing — and in what circumstances — is a question for a clinical genetics service rather than a self-referral. Your oncologist can advise whether a genetics referral is appropriate for your family.

Ask directly before treatment starts: 'Is my chemotherapy a fluoropyrimidine, and if so, has DPD testing been considered?' That question is specific and entirely appropriate to raise. If DPD testing is not available at your centre, that does not mean your care is inadequate — practice varies across India and the evidence continues to develop. But the question is worth asking, and a clear explanation of what is and is not available to you is reasonable to expect.