S-1 + bevacizumab + raltitrexed

S-1 + bevacizumab + raltitrexed is a combination chemotherapy regimen composed of three agents: - **S-1** is an oral fluoropyrimidine derivative that combines tegafur (a prodrug of 5-fluorouracil), gimeracil, and oteracil potassium. It acts as an antimetabolite, inhibiting DNA synthesis by increasing the blood concentration of 5-FU and reducing gastrointestinal toxicity. S-1 is primarily used in the treatment of various carcinomas including gastric, colorectal, and pancreatic cancers[5]. - **Bevacizumab** is a recombinant humanized monoclonal antibody targeting vascular endothelial growth factor A (VEGF-A). By binding to VEGF-A, it inhibits angiogenesis—the formation of new blood vessels—thereby restricting tumor growth. - **Raltitrexed** is a folate analog antimetabolite that selectively inhibits thymidylate synthase, leading to impaired DNA synthesis and cell death. It is used mainly for advanced or metastatic colorectal cancer when other fluoropyrimidine-based therapies are unsuitable[6][8]. This combination targets both tumor cell proliferation (via inhibition of thymidylate synthase and DNA synthesis) and tumor angiogenesis (via VEGF inhibition). The regimen may be considered for advanced or metastatic colorectal cancer patients who are not candidates for standard regimens containing oxaliplatin or irinotecan.