The microbiome–cancer axis: microbial biomarkers across gastrointestinal malignancies

Microbial markers are increasingly recognized as effective tools for the early detection and management of gastrointestinal (GI) cancers, reshaping strategies for diagnosis and treatment. These biomarkers include diverse molecules and bacterial cells, each with distinct roles in diagnosis, prognosis, and therapeutic monitoring. This review consolidates information from studies on colorectal, gastric, esophageal, and pancreatic cancers, highlighting common microbial trends and their importance in clinical settings. Prominent microbial markers like Fusobacterium nucleatum in colorectal cancer, Helicobacter pylori virulence factors in gastric cancer, and oral anaerobic bacteria in esophageal cancer are emphasized as specific biomarkers at different stages. We discuss the diagnostic and prognostic value of microbial biomarkers and their impact on treatment response. By combining microbial information with genomic and clinical factors, microbial biomarkers present non-invasive approaches for cancer prevention and personalized medicine. Finally, we address challenges in biomarker validation and translation, underscoring their potential to transform GI cancer diagnostics and therapy.