In the human gut, there are many microbes, including bacteria, viruses and parasites. The imbalance in the numbers of each type of these microbes can translate into gastrointestinal disorders. Lately, different microbiota patterns have been associated with the levels of efficacy of immunotherapy in multiple cancer conditions. Studies have shown that patients with a more diverse gut microbiome respond better to immunotherapy than those with a homogeneous microbiome. This systematic review aims to identify and assess the available evidence on the efficacy of immunotherapy in treating colorectal cancer (CRC) patients and the effect of their microbiota on their treatment outcomes. The researchers will study the literature regarding CRC and immunotherapy outcomes to survey the different approaches employed to assess the treatment outcomes. A systematic search will be performed in five biomedical databases (PubMed, Scopus, Web of Science, Embase, and the Cochrane Library) in June-July, 2022. Also, open-access registers of clinical trials will be trawled. The search will be conducted without geographical or publication date restrictions; however, only papers published in the English language will be sought. Details regarding patients’ diets, lifestyles, and characteristics will be assessed. We will define the primary outcome to compare CRC patients’ immunotherapy responses with their gut microbiota composition. The systematic review methodology does not require ethics approval due to the nature of the study design. The systematic review results will be published in an open-access peer-reviewed journal.
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