Human Microbiome Influence on Head and Neck Cancer

• Gut microbiome dysbiosis contributes to HNC initiation and progression. • Specific bacterial taxa modulate inflammation and immune responses. • Microbial metabolites influence oncogenic signalling pathways. • Microbiome profiles show promise as diagnostic biomarkers in HNC. • Targeting dysbiosis may enhance future therapeutic strategies. Recent breakthroughs in microbiome research have identified the gut microbiota as an important regulator of systemic immunity, inflammation, and carcinogenesis. Although established risk factors for head and neck cancer (HNC) include tobacco use, alcohol use, and human papillomavirus (HPV) infection, growing data suggest that gut microbial dysbiosis may also play a role in its etiology. Changes in gut microbiota composition can have a distal influence on the head and neck region by modulating immune function, producing microbial metabolites, and disrupting epithelial barrier integrity, influencing tumor initiation, development, and therapeutic response. New research suggests that the gut microbiome plays an important role in regulating the success and toxicity of traditional HNC treatments such as chemoradiation and immunotherapy. This review focuses on current evidence linking alterations in the gut microbiome to HNC development and progression, emphasizing underlying mechanisms, diagnostic potential, and emerging microbiome-based therapeutic strategies.