Intratumoral microbiota as prognostic biomarkers in gastrointestinal cancers

Recent evidence highlights that the tumor microenvironment in gastrointestinal (GI) cancers harbors distinct microbial communities with potential prognostic value. GI malignancies account for nearly 25% of all cancer-related deaths worldwide, yet patients with comparable histopathological features often display markedly different clinical outcomes. Emerging multi-omics studies involving over 3000 tumor specimens have revealed that specific microbial taxa, including Granulicella, Fusobacterium nucleatum, and Parvimonas micra, are linked to advanced disease stages, lymphatic spread, and poorer overall survival. F. nucleatum, in particular, has been implicated in promoting chemoresistance via Toll-like receptor 4 activation and modulation of the immune microenvironment. Reduced microbial alpha diversity within tumors has also been correlated with disease aggressiveness, suggesting a dysbiosis-mediated influence on tumor immunity. Integration of microbial profiles with transcriptomic and immunologic datasets has produced hybrid models that outperform conventional TNM staging in predicting recurrence and therapy response. Standardizing sampling, sequencing, and analytical methodologies remains a critical challenge. The incorporation of microbiome profiling into diagnostic and registry systems could enable routine use of intratumoral microbial signatures as prognostic biomarkers, paving the way toward microbiome-informed precision oncology.