Microbiota Alterations in Precancerous Colon Lesions: A Systematic Review

Simple Summary Even with recent advances, gut microbiota is still one of the most demanding challenges that research needs to handle. In particular, given its deep impact on gastrointestinal health, microbiota could explain the development and progression of certain diseases. Moreover, it could be used as a potential predictive biomarker. Given this, the relationship between intestinal microbiota and colorectal adenoma, considered a premalignant lesion leading to carcinoma, has been deeply evaluated. This review highlights the historical and novel data on microbiota characteristics in adenoma patients to provide an updated summary of current knowledge and its limits. Gut microbiota plays an important role in human health. It may promote carcinogenesis and is related to several diseases of the gastrointestinal tract. This study of microbial dysbiosis in the etiology of colorectal adenoma aimed to investigate the possible causative role of microbiota in the adenoma-carcinoma sequence and its possible preventive role. A systematic, PRISMA-guided review was performed. The PubMed database was searched using "adenoma microbiota" and selecting original articles between January 2010 and May 2020 independently screened. A higher prevalence of Proteobacteria, Fusobacteria, and Bacteroidetes phyla was observed in the fecal luminal and mucosa-associated microbiota of patients with adenoma. However, other studies provided evidence of depletion of Clostridium, Faecalibacterium, Bacteroides and Romboutsia. Results on the relationship between adenoma endoscopic resection and microbiota were inconsistent. In conclusion, none of the analyzed studies developed a predictive model that could differentiate adenoma from non-adenoma patients, and therefore, to prevent cancer progression. The impact of adenoma's endoscopic resection on microbiota was investigated, but the results were inconclusive. Further research in the field is required.