Fluorouracil (5-FU) is one of the most successful and widely used chemotherapy drugs. It is often used in the treatment of breast, colon, and skin cancer (three of the most frequently occurring cancers).
In general, 5-FU is relatively well tolerated at standard doses. However, an estimated 3-5% of patients have a genetic variation that leads to a deficiency of an enzyme called dihydropyrimidine dehydrogenase (DPYD) that is crucial for the metabolism and deactivation of 5-FU. Patients with this variation have severe toxic reactions that may be fatal with even small doses and often the very first dose of 5-FU.
Who should be Tested for 5-FU Deficiency
Pharmacogenetic testing, specifically the DPYD (DPD) test for 5-FU is considered appropriate for any person who is taking or considering 5-FU based chemotherapy.
It is recommended that this screening is accompanied by direct measurement of DPYD activity prior to 5-FU treatment in cancer patients. Although this test screens for the most frequent genetic variation that causes DPYD enzyme deficiency this does not rule out the possibility of a decrease in DPYD activity due to other factors or genetic variations.