Microbiome modulation in the prevention and management of colorectal cancer: a systematic review of clinical interventions

INTRODUCTION: The role of probiotics/prebiotics in modulating the procarcinogenic effects of microbiota have been studied with inconclusive results. This systematic review aimed to identify the role of several studied interventions on the gut microbiota modulation in humans for the prevention and management of colorectal cancer (CRC). METHODS: We conducted a systematic search using PubMed and Cochrane Central electronic databases, identifying clinical studies published within the last 20 years. We performed a qualitative analysis of eligible studies included in our review on each of the 4 investigated topics: CRC potential biomarkers, dietary interventions, probiotic administration in non-surgical and surgical patients, respectively. RESULTS: A total of 54 studies involving healthy volunteers, in addition to colorectal adenoma and CRC patients were included in our qualitative synthesis. We were able to identify bacterial signatures of CRC including Fusobacterium nucleatum and Clostridium butyricum. Moreover, dietary supplementation with oligosaccharides or fibers increased short chain fatty acid-producing bacteria levels, thus inhibiting tumorigenesis. Furthermore, we have confirmed that Lactobacilli and Bifidobacterium intake modulates gut microbiota towards tumor suppression. We have also showed that probiotic intake around colectomy significantly reduces complications. CONCLUSIONS: Bacterial metabolism is strongly linked with colonic carcinogenesis and influenced by diet. Probiotics and prebiotics can act as microbiota modulators, suppressing epithelial proliferation and reversing DNA toxicity. As adjuvants to surgery or chemotherapy, Lactobacilli and Bifidobacteria decrease complications. Improved outcomes in CRC patients can possibly be achieved through future research directed towards the benefits of bacterial agents as tumor suppressors or as treatment of oncological therapy resistance.