DPYD and colorectal cancer: An important anticancer agent widely used in the treatment of colorectal cancers, 5-fluorouracil (5-FU), is catabolised rapidly to the inactive metabolite dihydrofluorouracil (FUH2) by the first and rate-limiting enzyme-dihydropyrimidine dehydrogenase (DPD) (Heggie et al, 1987).