Periodontopathogens in oral cancer: a meta-analysis of bacterial taxa of the oral microbiome associated with risk factors of oral squamous cell carcinoma

This study aims to investigate the distribution of microbial taxa that are present in abundance in the oral cavity of patients diagnosed with Oral Squamous Cell Carcinoma (OSCC). We begin with a search for relevant literature on the OSCC microbiome in electronic databases (PubMed and Google Scholar). From the identified literature, studies were considered for data extraction based on an inclusion criteria according to PRISMA guidelines. From an initial 1217 published studies, a total of 15 relevant studies were identified that fulfilled the inclusion criteria. These studies were conducted for the detection of microbial taxa in the oral cavities of patients with OSCC by correlation with healthy controls for differential microbial abundance. The data from the selected studies provided evidence on microbial taxa in different anatomical sites of the oral cavity i.e. gingival region, tongue, buccal site and floor of the mouth. The most common method for the detection of microbial flora in the literature was 16s rRNA sequencing. Only those studies from the literature were considered for further analysis that showed the association of risk factors i.e. tobacco smoking and smokeless, betel quid, alcohol and periodontitis with OSCC. Risk factors in the resulting 6 studies showed a strong odds ratio (OR) with statistical significance (p-value <0.05). The calculated risk ratio (RR) of these risk factors also demonstrated substantial heterogeneity. These studies showed an increase in the abundance of periodontopathogens belonging to the genus Fusobacterium, Capnocytophaga, Prevotella, Parvimonas and Porphyromonas. The microbial taxa associated in abundance with risk factors of OSCC such as smoked or smokeless tobacco, betel quid and alcohol were quite similar to the microbial taxa that cause periodontitis. The detection for abundance of periodontopathogens in OSCC a class of putative biomarkers at early stages of tumor development in OSCC, in individuals exposed to these risk factors.