A China-based study found mouth bacteria more common in the guts of gastric cancer patients, pointing to a possible oral-gut cancer link that needs more research.
Mouth bacteria may be moving into the gut in ways linked to stomach cancer, according to new research that adds to growing interest in how the microbiome may influence cancer risk.
The study, published in Cell Reports Medicine , found oral microbes more commonly in the guts of patients with gastric cancer than in patients with chronic gastritis. The findings point to a possible oral-gut pathway in cancer development, but the study was cross-sectional, meaning it can show an association, not prove that the bacteria caused cancer.
China-based researchers with BGI Genomics analyzed 404 samples from Chinese patients with gastric cancer and chronic gastritis. They studied gut microbiome samples from stool, along with oral microbiome samples from saliva and the tongue.
The researchers reported differences in gut microbes among gastric cancer patients, identifying 28 gut species that varied. Most were oral bacteria, including Streptococcus , lactobacillus and other lactic acid bacteria.
Twenty oral-gut species were found in both saliva and stool and were more common in the guts of gastric cancer patients. Genetic comparisons showed the oral bacteria closely matched gut bacteria in the same person, suggesting the microbes may have traveled from the mouth to the gut.
The researchers said saliva and stool samples could eventually help identify microbial patterns associated with stomach cancer. For now, however, they said more work is needed before such testing could be used in routine care.
Dr. Brian Slomovitz, director of gynecologic oncology and co-chair of the Cancer Research Committee at Mount Sinai Medical Center in Miami Beach, Florida, told Fox News Digital that the study fits an “initiator-promoter” model of cancer development. He was not involved in the research.
“It is very important that we work toward a healthy microbiome in the gut to decrease the risk of inflammation and cancer,” Slomovitz said.
He said inflammation is often the initiating factor in gastric cancers, including inflammation linked to H. pylori infection. In that model, damaged mucosal cells may then create conditions where lactic acid-producing bacteria can colonize, potentially helping explain why some cancers develop even after H. pylori treatment.
Slomovitz said the findings could help lay groundwork for early detection research using saliva, including detection in precancerous states. But he cautioned against applying the findings too quickly: “However, we are not ready to incorporate this into clinical practice.”
Fox News senior medical analyst Dr. Marc Siegel also noted that awareness of the gut microbiome’s role in overall health has been increasing, including its possible relationship to cancer risk.
The next question for researchers is whether the microbial pattern is merely a marker of disease or part of the biological process that helps gastric cancer develop. Until that is clearer, the findings remain a signal for further study rather than a basis for screening or treatment changes.
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