The influence of the gastrointestinal microbiome on colorectal metastasis: a narrative review.

Abstract

The gastrointestinal microbiome has been suggested to contribute to the development of both primary and secondary colorectal cancer. Despite advances in understanding the prognostic and predictive value of clinico-pathological parameters, the underlying mechanisms that result in progression to metastatic disease have yet to be defined. The metastatic cascade involves a number of sequential steps, including detachment of tumour cells from the primary site, intravasation and dissemination within the circulatory and lymphatic systems, with extravasation and proliferation at a secondary site. An analysis of the literature relating to the gastrointestinal microbiome and its role in colorectal metastasis was conducted. This review aims to examine the current evidence supporting a role for the microbiome in colorectal metastasis and to describe the mechanisms by which it may contribute to metastatic progression. The invasive pathways utilized by bacteria and how they may be manipulated by tumour cells for migration and metastasis are presented and the potential of the intestinal microbiome as a therapeutic target in colorectal carcinogenesis and metastasis is detailed here.