Objective: Colorectal cancer is one of the most frequently diagnosed cancers worldwide. Scientific evidence suggests a relationship between gut microbiota and colorectal cancer occurrence and development. In addition, recent findings corroborate the assumption that probiotics administration could represent a valuable adjuvant therapy to manage gut dysbiosis and to prevent side effects of anticancer therapies.

Materials and Methods: A review of the literature concerning the role of gut microbiota, microbial metabolites and probiotics in CRC prevention and treatment with a special emphasis on the mechanism of action and evidence on both animals and humans was conducted. PubMed/Medline, Google Scholar, EMBASE, and the Cochrane Library supplemented with ScienceDirect.com (Elsevier), Wiley Online, SpringerLink, and Cambridge Journals were used as search engine and browsers. None language restriction was applied, and all studies published up to November 2019 have been considered.

Results: The analysed data showed that both gut microbiota and microbial metabolites play an important role in colorectal cancer occurrence and development. In vitro and in vivo studies suggest that probiotics exert intraluminal and systemic colorectal cancer-preventative effects. In addition, human clinical trials revealed that probiotics have inhibitory effects on the development of cancerous and precancerous lesions along with features to manage cancer treatment side effects.

Conclusions: More in-depth studies should be carried out in order to better understand the interactions between host and pathogens correlated with colorectal carcinogenesis. Even though the in vivo results demonstrate the beneficial effect of probiotics in alleviating the anticancer therapies side-effects, further randomized double-blind, placebo-controlled clinical trials are strongly required to fully understand the probiotics’ action and to recommend their routine use as adjunctive therapy for colorectal cancer prevention and treatment.