Gut Microbiota and Central Nervous System Tumors: A Comprehensive Systematic Review and Meta-Analysis of...

The gut-brain axis has emerged as a critical pathway influencing central nervous system (CNS) tumor biology through complex microbiome-mediated mechanisms. Understanding these interactions is essential for developing novel therapeutic strategies and biomarkers for CNS tumors. To systematically review and meta-analyze current evidence on gut microbiota interactions with CNS tumors, examining mechanisms, clinical correlations, therapeutic implications, and biomarker potential. We conducted a comprehensive systematic review following PRISMA guidelines, searching PubMed, EMBASE, Google Scholar, and Cochrane Library databases for studies published from 2010-2025. A random-effects meta-analysis of reported statistical outcomes was performed to quantify microbiome alterations using standardized mean differences (Cohen's d) and diagnostic accuracy measures. Analyses were based on published summary statistics rather than reprocessed raw sequencing data, acknowledging cross-study heterogeneity. From 161 identified records, 12 studies met inclusion criteria (6 clinical studies, n = 387 participants; 6 preclinical studies). Meta-analysis revealed significant Shannon diversity reduction in CNS tumor patients (Cohen's d = -1.237 [95% CI: -1.614, -0.860; 95% PI: -2.48, -0.12]) with moderate heterogeneity (I² = 60.5%). Evidence demonstrated significant gut microbiome alterations with reduced microbial diversity, increased pathogenic bacteria (Akkermansia muciniphila: 2.23-fold increase, Fusobacterium spp.: 2.04-fold increase), and decreased beneficial bacteria (Bifidobacterium spp.: 47% reduction, Lachnospira spp.: 56% reduction). Diagnostic performance showed fair discrimination (pooled AUC = 0.786 [95% CI: 0.781, 0.791]). Key mechanisms include bidirectional tumor-microbiota interactions through immune system modulation, metabolic pathway alterations involving short-chain fatty acids, and inflammatory response modifications within the altered CNS immune privilege environment. Preliminary evidence suggests gut microbiota alterations in CNS tumor patients, but findings require validation in large, standardized cohorts before clinical application. Current evidence quality is low (GRADE assessment), necessitating substantial additional research.