fluorouracil + folinic acid + filgrastim

A combination chemotherapy regimen consisting of **fluorouracil (5-FU)**, **folinic acid (leucovorin)**, and **filgrastim (G-CSF)**. Fluorouracil is an antimetabolite that interferes with DNA and RNA synthesis by inhibiting thymidylate synthase and incorporating its metabolites into DNA and RNA, leading to cytotoxic effects in rapidly dividing tumor cells[4]. Folinic acid is a reduced form of folic acid that enhances the binding of 5-FU metabolites to thymidylate synthase, thereby enhancing the cytotoxic activity of fluorouracil[3][5]. Filgrastim is a recombinant granulocyte colony-stimulating factor (G-CSF) that stimulates the production of neutrophils, used to prevent or treat neutropenia caused by chemotherapy, or to allow dose-dense regimens[4][7]. This combination may be selected for regimens requiring neutrophil support or dose intensification, particularly in the treatment of gastrointestinal malignancies such as colorectal, gastric, or rectal cancer.