Systematic Review of Fecal and Mucosa-Associated Microbiota Compositional Shifts in Colorectal Cancer

Background: Gut microbiota fulfill a vital role in colorectal cancer. The aim of this study was to systematically review all the existing literature on the association of mucosa-associated and fecal microbiota with the incidence, location, and stage of both colorectal adenoma and carcinoma. Methods: The scientific search was conducted up to July 2018. Among a total of 616 articles, 54 fulfilled the inclusion and exclusion criteria and were reviewed. The Newcastle-Ottawa Scale (NOS) for surveying the standard was utilized for quality control. Results: A total of 54 articles were incorporated in the study. Fusobacteria 39 (72%), Firmicutes 22 (40%), Bacteroidetes 19 (35%), Proteobacteria 15 (27%), and Actinobacteria 10 (18%) were the most prevailing phylum that were found in colorectal cancer patients. Among these taxa, some of them grew more in colorectal cancer patients in contrast with the control; conversely, some taxa such as Collinsella, Pedobacter, Bifidobacterium, Megamonas, Brevundimonas, Burkholderia were less prevalent in colorectal cancer patients. Moreover, in some taxa like Prevotella, Alistipes, Lachnospiraceae, Subdoligranulum, Roseburia, Ruminococcus, Eubacterium, Dorea, Bacillus, Parvimonas, Faecalibacterium, Dialister, Staphylococcus, Lactobacillus, Enterococcus, Blautia, Escherichia coli, and Pseudomonas, there have been controversies among specialists. Conclusion: Until now, several studies have incontestably reported the potential role of gut microbiota to be used for the detection of colorectal cancer; however, there are no predefined protocols. In this article, we attempted to summarize and organize articles that have investigated the microbiota as a type of strategy for screening colorectal cancer.