Gut microbiome in surgical oncology: mechanisms, perioperative outcomes, and therapeutic opportunities

The gut microbiome is a fundamental determinant of gastrointestinal physiology. It is essential in maintaining host homeostasis while also implicated in cancer pathogenesis and alteration in physiological response to surgical stress. The aim of this narrative review was to evaluate the microbiome's mechanistic role in surgical oncology, assessing it as a biomarker for risk stratification and an emerging therapeutic target.

The current literature was synthesized to examine microbial impacts on tumorigenesis and perioperative surgical outcomes across the lower and upper gastrointestinal tracts (including the gut-lung axis), the hepatopancreatobiliary system, and extra-abdominal malignancies (breast cancer and melanoma).

Dysbiotic microbial signatures, termed the oncobiome, actively drive tumour progression and immune evasion. Perioperative interventions induce acute microbial shifts linked to serious complications such as anastomotic leaks and pneumonia. Clinically, targeted modulation yields significant benefits, as demonstrated by perioperative synbiotics reducing infectious complications by up to 45% in colorectal surgery and 64% in major liver surgery. Furthermore, preoperative oral care reduces post-oesophagectomy pneumonia by up to 50%, while Helicobacter pylori eradication halves metachronous gastric cancer risk. However, a detrimental 'antibiotic paradox' exists in melanoma, where pretreatment antibiotic exposure severely impairs immune checkpoint inhibitor efficacy. Conversely, faecal microbiota transplantation can reverse this immunotherapy resistance, achieving up to 80% response rates in trials.

The microbiome is a critical, modifiable determinant of both short-term surgical recovery and long-term oncological survival. Future surgical oncology practice will need to integrate precision surgical microbiome-mediated biotherapeutics to optimize outcomes in multidisciplinary cancer care.