S-1 + bevacizumab + leucovorin

S-1 + bevacizumab + leucovorin is a combination chemotherapy regimen used primarily in the treatment of metastatic colorectal cancer (mCRC). - **S-1** is an oral fluoropyrimidine derivative composed of tegafur (a prodrug of 5-fluorouracil), gimeracil, and oteracil potassium. It increases the blood concentration of 5-FU while reducing gastrointestinal toxicity. - **Bevacizumab** is a recombinant humanized monoclonal antibody that inhibits vascular endothelial growth factor A (VEGF-A), thereby blocking angiogenesis required for tumor growth. - **Leucovorin** (folinic acid) enhances the cytotoxic effects of fluoropyrimidines like 5-FU by stabilizing their binding to thymidylate synthase. This combination aims to maximize antitumor efficacy by combining cytotoxic chemotherapy with antiangiogenic therapy and biochemical modulation. Clinical studies have shown that regimens including S-1, bevacizumab, and leucovorin are effective and generally well-tolerated in patients with mCRC[2][3].