Gut Bacterial Microbiome Profiles Associated with Colorectal Cancer Risk: A Narrative Review and Meta-Analysis

Abstract

Objective: Recent studies have shown a potential link between the gut microbiome and colorectal cancer (CRC). A wide array of research into this topic was performed over the past decade, illustrating a keen interest in the potential causal relationship between the gut microbiome and CRC. However, the cancer research community is lacking a concise review of this kind, which aims to explore the evidence linking the human gut microbiome to the risk of developing CRC. Design: This narrative review was carried out by two independent reviewers who assessed the database outcomes from Medline and EMBASE during May 2020. A meta-analysis was undertaken to study the link between Helicobacter pylori and CRC. The meta-analysis was processed through Stata (StataCorp LLC, Lakeway Drive, College Station, Texas, USA). Results: Thirty one papers were included in this narrative review, of which 12 were included in the meta-analysis. From these papers, Fusobacterium and Bacteroides were reported most frequently as enriched in those with CRC versus the control populations. The meta-analysis showed an odds ratio of 1.49 (95% CI: 1.19–1.86), including a total of 20,001 events. This meta-analysis concluded that H. pylori infection significantly increases the risk of CRC, albeit with evidence of publication bias. Conclusion: Bacteria have been found to increase the risk of CRC; however, a definitive causal relationship cannot be concluded or excluded using case-control studies. To fully understand the potential link of the bacteria listed, alterations in research design and execution are required. The assessment found a need for a large-scale cohort study conducted over a significant period of time to thoroughly evaluate the potential relationship between gut microbiome and CRC risk.