5-[18F]Fluorouracil

**Semantic type:** Pharmacologic Substance

**Definition:** The fluorine-18 (18F)-radiolabeled pyrimidine analog 5-fluorouracil (5-FU) with positron-emitting activity. Upon administration, 5-[18F]fluorouracil distribution in tumor tissue may be measured with positron emission tomography (PET). The degree of 5-[18F]fluorouracil uptake in tumor tissue may help to predict the response to 5-fluorouracil-based chemotherapy or to determine the response to other therapeutic agents used to treat 5-FU-sensitive tumors.