Colorectal cancer (CRC) has become a serious threat to human life and health. Most patients are diagnosed at the late stage of advanced CRC, resulting in losing their best opportunity for surgical treatment. Chemotherapy plays a crucial role in the control and treatment of advanced CRC. However, the cytotoxicity of chemotherapeutic drugs can easily cause the imbalance of gut flora, damage the barrier of the gastrointestinal mucosa, and mediate mucosal inflammation of the digestive tract, which is called “gastrointestinal mucositis.” This mucositis can affect the quality of life of the host and even threaten their lives. Several studies reported the association between chemotherapy-mediated gastrointestinal mucositis in CRC and gut dysbiosis. However, the underlying mechanisms of this association are still unclear. The alternative or complementary treatments to reshape gut microbiota and slow down the side effects of chemotherapy have shown the improvement of gastrointestinal mucositis following chemotherapy in the CRC condition. This review will summarize and discuss the evidence of the association between chemotherapy-mediated gastrointestinal mucositis in CRC and altered gut microbiota from in vivo and clinical studies. The possible mechanisms of gastrointestinal mucositis, including the destruction of the gastrointestinal mucosal barrier, the induction of gut dysbiosis, and histopathological changes in the gut of CRC with chemotherapy will be illustrated. In addition, the nonpharmacological interventions and phytochemical extracts by using the manipulation of the microbial population for therapeutic purposes for relieving side effects of chemotherapy as well as a cancer treatment would be summarized and discussed in this review.

结直肠癌（CRC）已成为严重威胁人类生命和健康的疾病。大多数患者在晚期 CRC 时被诊断出来，导致他们失去了手术治疗的最佳机会。化疗在晚期CRC的控制和治疗中起着至关重要的作用。但化疗药物的细胞毒性易引起肠道菌群失调，破坏胃肠道黏膜屏障，介导消化道黏膜炎症，称为“胃肠道黏膜炎”。这种粘膜炎会影响宿主的生活质量，甚至威胁到他们的生命。几项研究报告了 CRC 中化疗介导的胃肠道粘膜炎与肠道菌群失调之间的关联。然而，这种关联的潜在机制仍不清楚。重塑肠道微生物群和减缓化疗副作用的替代或补充治疗表明，结直肠癌化疗后胃肠粘膜炎得到改善。本综述将总结和讨论结直肠癌化疗介导的胃肠道粘膜炎与肠道菌群改变之间关联的证据。体内和临床研究。将阐述胃肠道粘膜炎的可能机制，包括胃肠道粘膜屏障的破坏、肠道菌群失调的诱导以及化疗导致 CRC 肠道的组织病理学变化。此外，本综述将总结和讨论非药物干预和植物化学提取物，它们通过操纵微生物群来缓解化疗和癌症治疗的副作用。