Patients with Colorectal Cancer

Abstract

Abstract:Background: Colorectal cancer (CRC) is one of the most common cancers in the Western world, with approximately 1.2 million people diagnosed worldwide each year. Most CRCs are sporadic, resulting from chromosome instability and dysplasia of adenomas to carcinomas. At the same time, the hereditary syndromes of familial adenomatous polyposis (FAP) and hereditary nonpolyposis colpos (HNPCC) arise due to germline mutations in the APC gene and the microsatellite instability pathway. Dysbiosis and associated chronic inflammation have previously been implicated in inflammatory bowel disease, irritable bowel syndrome, and type 2 diabetes mellitus. They are now known to facilitate carcinogenesis in CRC through genetic and epigenetic mechanisms. The dysbiotic bacterium primarily implicated in CRC is Fusobacterium nucleatum, associated with microsatellite instability and lymph node metastasis in clinical trials. Recent clinical studies have also suggested that they may affect prognosis, which, if established, could potentially signal a new frontier in the diagnosis, evaluation and therapeutic management of CRC. Objectives: To systematically review the literature to gather evidence investigating the associations between gut microbiota and CRC, colorectal adenomas, CRC tumour site, CRC stage, prognosis and survival, and the effect of current therapy performed for the treatment of CRC. Methodology: A systematic review of the published literature. Results: 53 studies were considered relevant for inclusion, covering a total of 5167 CRC patients, of which 3754 were tested through mucosal tissue samples, 1072 through stool samples and 341 through a combination. Conclusion: There is a significant association between gut microbiome and CRC, with emphasis on Fusobacterium (genus) and F. nucleatum (species). This association appears to exist more in advanced stages of the tumour and/or adenoma and is often associated with worse prognosis and shorter survival.Keywords: Colorectal cancer, familial adenomatous polyposis, Fusobacterium nucleatum, intestinal microbiota