Oral Microbiome as a Biomarker and Therapeutic Target in Head and Neck Cancer: Current Insights and Future Directions

Background/Objectives: The oral microbiome has been implicated in the pathogenesis of head and neck squamous cell carcinoma (HNSCC). This review examines the association between specific oral bacterial taxa and HNSCC. Methods: A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to examine the relationship between the oral microbiome and HNSCC. A comprehensive literature search was conducted in databases including EMBASE, Cochrane Library, Web of Science, Medline, and PubMed. Results: Following the screening of 284 articles, 21 studies met the inclusion criteria, comprising 1023 HNSCC patients (male: n = 806, 79%; female: n = 217, 21%) and 837 healthy controls (male: n = 622, 74%; female: n = 215, 25.7%). Although findings on alpha diversity were inconsistent, a significant difference in beta diversity was consistently reported between HNSCC patients and healthy controls. HNSCC patients exhibited higher relative abundances of Firmicutes and Synergistetes at the phylum level; Fusobacterium, Prevotella, Porphyromonas, Parvimonas, and Peptostreptococcus at the genus level; and Fusobacterium nucleatum, Prevotella intermedia, Lactobacillus spp., and Porphyromonas gingivalis at the species level. In contrast, healthy controls showed higher abundances of Proteobacteria and Actinobacteria at the phylum level; Streptococcus, Actinomyces, Corynebacterium, Rothia, and Veillonella at the genus level; and Haemophilus influenzae, Rothia mucilaginosa, and Streptococcus mitis at the species level in most studies. Conclusions: The findings indicate distinct alterations in oral microbiome diversity and composition among HNSCC patients, highlighting the role of microbial dysbiosis in cancer progression. Standardized protocols for oral sample collection and microbiota analysis are essential to facilitate more robust, comparable, and clinically meaningful research outcomes.