A new study has revealed promising indicators in oral bacteria that may help in the future to detect some types of cancer, through a simple, non-invasive sample collected using mouthwash.
Scientists have known for years that the mouth is not only linked to the health of the teeth and gums, but can also reflect various aspects of overall health. The gums, tongue, and teeth harbor a large and diverse population of bacteria, and changes in these areas have been linked to a number of health conditions, including heart disease, anemia, and infections.
In the new study, scientists in South Korea examined oral and stool samples from more than 500 people, including healthy individuals and others with metabolic disorders such as diabetes and high blood pressure, as well as patients with stomach cancer and colorectal cancer.
The researchers analyzed the DNA of microbes found in the samples using gene sequencing technology, and then developed an index they called the "mouth-fecal similarity index" (MF), with the aim of measuring the degree of similarity between bacteria found in the mouth and those found in the intestines.
The results showed a clear difference between the groups, with patients with stomach, colon, and rectal cancer exhibiting distinct microbial patterns, along with a significant increase in the oral-fecal similarity index. This same increase was not observed in individuals with metabolic disorders.
To verify the significance of these indicators, the scientists compared the results with the fecal occult blood test, a test used to screen for colorectal cancer. Samples taken from the mouth showed a greater ability to distinguish between cancer patients and healthy individuals in the study.
Models based on oral swab data were also able to distinguish between cancer patients and healthy individuals in different groups. The association between microbial markers and cancer remained even after accounting for lifestyle factors such as alcohol consumption, exercise, and body mass index.
Study co-author Sun Ha Ji of Yonsei University said that the presence of oral-associated bacteria in the intestines of cancer patients was not entirely surprising, but scientists did not anticipate how much the microbial signals would differ between patient groups, or how much information could be obtained from oral samples alone.
The researchers believe that these results may pave the way for the development of new screening methods for gastrointestinal cancers that are simpler and less invasive than some current methods.
The team plans to conduct further studies on people who have not yet been diagnosed with cancer, with the aim of verifying the results and determining whether the transfer of bacteria between the mouth and intestines may be involved in the development of cancer, or whether it occurs as a result of having it.
The method is still in the research phase and requires further studies and clinical trials before it can be widely used. If future research confirms the findings, collecting a mouth sample using a simple mouthwash could become an easy and minimally invasive option, potentially expanding the scope of early detection screenings for certain gastrointestinal cancers.
