Oral Microbiome Changes Associated With Lung Cancer in Non-Smokers

An observational study performed on two groups of nonsmoking subjects with all matching criteria except for the abundance of the oral microbiota. The study found that the group with the lower oral microbiota diversity developed cancer in the long run, hence hinting at a causal-effect relationship between the two.

Lung Cancer

The human oral microbiome refers to the microorganisms that are naturally found in the human oral cavity. Some of the predominant microorganisms include Streptococcus, Granulicatella, Gemella, and Veillonella species. This microbiome is vital for the good health of the oral cavity as it can cause oral and systemic diseases if its state of equilibrium is disturbed.

The microorganisms exist in the oral cavity in a state of balance and do not act as pathogens when in such a state. However, if any stimuli, external or internal, were to disturb this balance, it could have both long term and short term negative effects.

In fact, the variability in oral microbiome or flora has been found to be associated with several types of cancers and neoplastic conditions. A new study has tried to find a connection between oral microbiota changes and lung cancer in non-smokers.

An Albert Einstein College of Medicine Study

Hosgood and Kluman, along with their research team, conducted an observational study with the purpose of finding a causal-effect relationship between the variety and abundance of oral microbiota and the incidence of lung cancer in non-smokers.

The team of researchers from Albert Einstein College of Medicine collaborated with scientists from Vanderbilt University, National Cancer Institute in Bethesda, and the National Cancer Institute in Shanghai to find the results which were published in the Thorax journal.

Method of the Study

Hosgood and his team designed the study to be a nested case-control study within two prospective cohort studies; Shanghai Women’s Health Study and Shanghai Men’s Health Study.

The subjects of the study were picked from these two cohorts and they all had to meet a list of certain criteria to be considered. The most important criterion set by the researchers for this study was that all subjects be life-long non-smokers. Before starting the study, they provided a mouth profile by rinsing out their mouth, which helped the researchers set a baseline for everyone’s oral microbiota.

The subjects then went through a follow-up every 2 years to be screened for lung cancer. The study was conducted between 1996 and 2006 which gave the researchers more than enough time to observe.

Results of the study

Hosgood and his team of researchers found that 114 of the total subjects developed lung cancer around 7 years from the start of the study, 90 of whom were females and 24 were males. The results divided the subjects into two groups, the group with lung cancer and the group without.

When the researchers analyzed the groups, they found that apart from the diagnosis of cancer, the only main difference between the two groups was the abundance of oral microbiota.

The researchers emphasize that this study was an observational study which means that they cannot conclusively link oral microbiome changes to lung cancer in nonsmokers but it can be the first step, perhaps in the right direction.

Hosgood and his team call for more studies to be performed on the possible connection that they have observed to be able to conclusively discuss the results.