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

ObjectiveRecent studies have shown a potential link between gut microbiome and colorectal cancer (CRC). Initially, a wide array of research into this topic was discovered from 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 summarised systematic review of this kind which aims to explore the evidence linking the human gut microbiome to risk of CRC. DesignThis systematic review was carried out with two independent reviewers assessing the database outcomes from Medline and EMBASE during May 2020. A meta-analysis was undertaken studying the link between Helicobacter pylori and CRC; processed through Stata. Results31 papers were included in the systematic review, followed by 12 for the meta-analysis. From these papers, Fusobacterium and Bacteroides were reported most frequently as enriched in CRC versus control. 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. ConclusionsBacteria have been discovered 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. O_TEXTBOXSignificance of studyWhat is already known on this subject? [tpltrtarr]Roughly 10% of all cancer deaths in the UK are attributed to colorectal cancer (CRC), with CRC being the third most common cancer worldwide. [tpltrtarr]The risk of developing CRC has been closely linked to the composition of the gut microbiome [tpltrtarr]H. pylori is a known causative agent of gastric cancer What are the new findings? [tpltrtarr]To the best of the researchers knowledge, this is the first systematic review of this type conducted into this topic, investigating the genera/species of bacteria in the human gut microbiome and the risk of CRC. [tpltrtarr]This systematic review found a strong association between Fusobacterium and Bacteroides, amongst other species, and CRC. [tpltrtarr]The meta-analysis found a significant link between H. pylori infection and increased risk of CRC. How might this impact on clinical practice in the foreseeable future? [tpltrtarr]This systematic review provides potentially actionable evidence in the personalised management of patients to reduce their risk of CRC. [tpltrtarr]This review has highlighted the need for a large population prospective cohort study, with standardised sampling methods. [tpltrtarr]The meta-analysis reinforces the importance of H. pylori testing and eradication in those deemed at high risk of CRC C_TEXTBOX