Peritoneal Metastases in Gastrointestinal Malignancies: A Review of the Pathophysiology of Metastasis and the Tumour Microenvironment

Peritoneal metastasis is a significant source of morbidity and mortality for patients with cancer from gastrointestinal origin such as gastric, colorectal, and appendiceal cancers, and treatment options are limited. Cross-sectional imaging is limited in sensitivity and specificity, and treating peritoneal metastases is limited by the bioavailability of systemic cytotoxic chemotherapy and metastatic burden. Within this review, we specifically explore the pathophysiology underlying peritoneal metastasis while emphasising the contributions of the tumour microenvironment and immune system.