The impact of the microbiome on colorectal cancer recurrence after resection

Surgical resection of a colorectal adenocarcinoma remains a cornerstone in its treatment. However, despite proper patient selection and neoadjuvant and/or adjuvant chemotherapy/radiation, up to 30% of patients thought to be cured will develop a postoperative recurrence. Unfortunately, the outcomes in patients who develop a postoperative recurrence are poor and are associated with high morbidity and mortality. The gut microbiome has emerged to play a role in virtually all aspects of human health. In this manuscript, we critically examine the current literature implicating the gut microbiome's role in the pathogenesis of postoperative recurrence after attempted curative resection. We discuss how microbes can drive a more advanced stage and explore how surgery itself can precipitate a gut microenvironment with tumorigenic bacteria and bacterial-derived metabolites that can drive postoperative tumor formation. Finally, we review evidence as to how the gut microbiome can be manipulated to improve oncological outcomes.