Fluorouracil (5-FU) is one of the most successful and widely used chemotherapy drugs. It is often used forof 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.