The type of bacteria in a person’s mouth could help determine whether they are at high risk of head and neck cancer, according to research that adds to the reasons for keeping good oral health.
The study, published in the journal JAMA Oncology, highlighted novel microbial risk factors that could single people out for personalized prevention strategies.
More than a dozen species of previously unrecognized oral bacteria were implicated, some of which had already been linked with the serious gum infections that make up periodontal disease.
A collective score involving 22 different bacterial types was associated with a 50% increased chance of developing head and neck squamous cell cancer (HNSCC).
“Our findings offer new insight into the relationship between the oral microbiome and head and neck cancers,” said lead researcher Soyoung Kwak, PhD, from the New York University Grossman School of Medicine. “These bacteria may serve as biomarkers for experts to flag those at high risk.”
Cancers of the oral cavity, pharynx, and larynx are disfiguring and linked with just a 60 percent chance of survival at five years and smoking, alcohol and human papillomavirus are all recognised risk factors.
However, attention has recently also focused on the role of other microbiota, possibly related to microbial metabolism of HNSCC carcinogens or to microbial factors associated with poor oral hygiene and periodontal disease.
To investigate further, researchers analyzed bacterial and fungal DNA from saliva samples collected in three studies of diverse U.S. residents that together tracked 159,840 individuals for a mean of 5.1 years.
Oral microbe DNA in 236 patients diagnosed with HNSCC were compared with 458 randomly selected study participants who had remained free from cancer.
While overall microbiome diversity at baseline did not relate to subsequent HNSCC risk, 13 oral bacterial species were associated with its development.
These species included Prevotella salivae, Streptococcus sanguinis, and Leptotrichia species, as well as several species belonging to beta and gamma Proteobacteria.
A combination of the red periodontal bacterial pathogen complex, including Treponema denticola, Porphyromonas gingivalis, and Tannerella forsythia, and the orange complex, including Fusobacterium nucleatum, Prevotella intermedia, Prevotella nigrescens, Eubacterium nodatum, Campylobacter showae, and Campylobacter gracilis, was linked with a moderately raised HNSCC risk, with an odds ratio of 1.06.
After accounting for factors known to play a role such as age, race, smoking and alcohol consumption, Kwak et al identified 22 oral bacterial species, including both commensals and periodontal pathogenic bacterial complexes, with an odds ratio of 1.50 per single increase in standard deviation.
There were no significant associations between oral fungi and HNSCC risk.
“This case-control study yielded compelling evidence that oral bacteria are a risk factor for HNSCC development,” the researchers concluded.
“The identified bacteria and bacterial complexes and the associated microbial risk score hold promise as potential biomarkers, along with other risk factors, to identify high-risk individuals for personalized prevention of HNSCC.”
