DPYD and cancer: In planning chemotherapeutic drugs, it is important to evaluate the cancer response against chemotherapy.17 The response rate of tumors to fluoropyrimidine drugs depends on thymidylate synthase and dihydropyrimidine dehydrogenase (DPD) activity.18 DPD is a main enzyme in the biochemical functions of the antimetabolite 5-FU as well as capecitabine.19-21