Modulating Cancer Immunotherapy Through the Intestinal Microbiota: Mechanisms, Clinical Evidence and the Emerging Role of Faecal Microbiota Transplantation

he human body contains a large number of bacteria, particularly in the intestine, which is home to approximately 1,000 species and 100 trillion bacteria.These intestinal bacteria regulate the immune system and are known to influence the efficacy of immune checkpoint inhibitors (ICIs), which play an important role in cancer medication.In recent years, many associations between the intestinal microbiota and cancer have been reported, and it has become clear that the intestinal microbiota may be a biomarker for cancer treatment and that the use of antibacterial drugs affects the intestinal microbiota and negatively affects the therapeutic efficacy of ICIs.An attempt to alter the intestinal microbiota is faecal microbiota transplantation (FMT), and it has been suggested that FMT may increase the response rate of ICIs.A safety trial of FMT therapy in combination with antibacterial agents for patients with cancer undergoing ICI is currently under way, and this trial is intended to evaluate safety and efficacy for future treatment development.