Introduction: Emerging evidence highlights the roles the gut microbiome and the immune system, integral parts of the gut-brain axis, play in developing various symptoms in cancer patients. The purpose of this systematic review was to describe the roles of inflammatory markers and the gut microbiome, as well as to describe their associations with psychoneurological symptoms and gastrointestinal toxicities in women with gynecologic cancers.

Methods: A comprehensive literature search was conducted in PubMed, Embase, and Web of Science from January 2000 to February 2021. The Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were utilized to screen the found articles. The quality of the included studies was assessed using the Mixed Method Assessment Tool. In the included studies, various inflammatory markers and gut microbiome diversity and patterns were measured.

Results: Sixteen studies met the eligibility criteria and were included in this systematic review. While there were discrepancies in the associations between various inflammatory markers and symptoms, most of the studies showed positive correlations between interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) and cancer-related psychoneurological symptoms and gastrointestinal toxicities in gynecologic cancer patients. Although there was no consensus in alpha diversity, studies showed significant dissimilarity in the microbial communities (beta diversity) in patients with gastrointestinal toxicities compared with patients without symptoms or healthy controls. Studies also reported inconsistent findings in the abundance of bacteria at different taxonomic levels. Radiation enteritis-derived microbiota could stimulate TNF-α and interleukin 1 beta (IL-1β) secretion.

Conclusions: Alteration of inflammatory markers, the gut microbiome, and their associations show emerging evidence in the development of psychoneurological symptoms and gastrointestinal toxicities in women with gynecologic cancers. More studies on the interactions between the immune system and the gut microbiome, two integral parts of the gut-brain axis, are required to shed light on the roles they play in symptom development.