The Gut Microbiome and Faecal Microbiota Transplantation in Brain Tumors: A Scoping Review

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BSTRACT

Gut microbiome dysbiosis can induce inflammation and immune suppression, potentially influencing the efficacy of chemotherapy, immunotherapy, and radiotherapy (RT). The gut–brain axis, immuno-oncology, and the gut microbiome are increasingly being studied as important factors in brain tumor biology and treatment response. A scoping review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews guidelines. Electronic databases (PubMed, SCOPUS, Central Register of Controlled Trials, and ScienceDirect) were searched, and, as per eligibility criteria, we included adults or children with primary or metastatic brain tumors and controlled animal models involving faecal microbiota transplantation (FMT) or native microbiome characterization. Outcomes assessed included overall survival, progression-free survival, immune biomarkers, microbiome composition, and tumor burden. Of 363 articles retrieved, four studies met the inclusion criteria. One human study of lung cancer patients with brain metastases found that RT responders possessed distinct microbial signatures ( Oscillibacter and Blautia ) compared to nonresponders ( Megamonas ). Preclinical findings demonstrated that antibiotic-induced dysbiosis accelerated glioma development and metastasis. FMT from healthy donors delayed tumor progression by modulating the immune microenvironment (e.g., Foxp3 expression), whereas FMT from patients with pituitary adenomas promoted tumor growth and immune escape (increased programmed death-ligand 1 and CD8+ infiltration). Though limited by small sample sizes, the current studies suggest a causal relationship between gut microbiome composition and brain tumor outcomes. While preclinical evidence supports the therapeutic potential of FMT to modulate the tumor-immune microenvironment, larger multi-center studies are required to validate these findings.