Fluorouracil and capecitabine, the backbone of colorectal cancer treatment. One enzyme clears most of the dose, and the small number of people who lack it can be harmed severely by an ordinary dose.
The clearest argument on this site for testing before a first dose rather than after a bad reaction. Fluorouracil and capecitabine are the backbone of colorectal cancer chemotherapy, and one enzyme — dihydropyrimidine dehydrogenase — clears most of what is given. People carrying no-function DPYD alleles clear very little, and standard doses have caused severe and fatal toxicity. CPIC publishes dose recommendations by genotype, and pre-treatment DPYD testing is now recommended before fluoropyrimidine treatment in several health systems. Nothing here is a reason to refuse chemotherapy; it is a reason for the test to happen before it starts.
CPIC Guideline for Dihydropyrimidine Dehydrogenase Genotype and Fluoropyrimidine Dosing: 2017 Update, Clinical Pharmacology & Therapeutics (PMID 29152729)
These are the positions in your own file that carry the genes above. Not every gene in a guideline is one we report — where that is the case the gene appears above without a variant here, and the note says so.
DPYD · rs3918290
Read more →DPYD · rs67376798
Read more →DPYD · rs75017182
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