Immunotherapy, which uses the body's immune system to fight cancer cells, has gained attention recently as a breakthrough in cancer treatment. Although significant progress has been made, obstacles still exist since cancers are skilled at avoiding immune monitoring. The gut microbiota is being looked at more and more in modern research as a critical component in improving the results of immunotherapy. Through modulating both innate and adaptive immune responses, the gut microbiome has a significant impact on cancer immunotherapy. The effectiveness of treatment and the way the immune system responds are significantly influenced by some microorganisms and the metabolites they produce, especially short-chain fatty acids. On the other hand, dysbiosis and persistent inflammation in the gut environment might unintentionally accelerate the growth of tumors, which makes the complex relationship between the makeup of the microbiota and cancer treatment more challenging. Gut microbiota plays a crucial role in immunotherapy effectiveness. Improved microbial diversity leads to better treatment responses, with some taxa like Bacteroides and Ruminococcaceae being linked to better responses to immune checkpoint inhibitors. Dysbiotic conditions can worsen immune-related side effects and reduce treatment effectiveness. Strategies manipulating gut microbiota, such as fecal microbiota transplantation, antibiotic therapies, and dietary interventions, could optimize immunotherapy response and prognosis. However, standardizing these interventions for different cancer types and patient populations is challenging due to individual microbiome differences. Future research should combine microbiome research with AI and rigorous clinical trials for individualized cancer treatments.
