dacarbazine + fluorouracil + semustine

This is a combination chemotherapy regimen consisting of three cytotoxic agents—dacarbazine, fluorouracil, and semustine—used in the treatment of advanced colorectal cancer. - **Dacarbazine** is an alkylating agent that acts as an antineoplastic by methylating guanine bases in DNA, leading to inhibition of DNA synthesis and function[2][6]. - **Fluorouracil (5-FU)** is a pyrimidine analog antimetabolite that inhibits thymidylate synthase, thereby blocking DNA synthesis[3][5]. - **Semustine** (methyl-CCNU) is a nitrosourea alkylating agent that causes cross-linking of DNA strands, inhibiting replication and transcription[7]. The combination has been studied in phase III clinical trials for patients with recurrent or metastatic colorectal carcinoma. The regimen aims to exploit synergistic effects between these agents to improve response rates compared to single-agent therapy or other combinations. However, studies have shown only modest improvements in response rate and survival with increased toxicity risk when using multi-drug regimens including these three drugs[1][4].