Doxifluridine, also known as 5'-deoxy-5-fluorouridine or 5'-DFUR, is a prodrug of the chemotherapy agent 5-fluorouracil (5-FU). It is a fluoropyrimidine nucleoside analog that is used in the treatment of various types of cancer, including colorectal cancer. Doxifluridine is designed to be more stable and less toxic than 5-FU, allowing for better absorption and distribution within the body. Once inside the cells, it is converted into 5-FU, which inhibits the synthesis of DNA and RNA, ultimately leading to the death of cancer cells. This drug is typically administered orally and has been shown to be effective in prolonging survival and improving the quality of life for patients with advanced colorectal cancer.