Researchers at Yonsei University have discovered that analyzing bacteria in saliva can help detect bowel cancer without requiring a colonoscopy or stool test.
The scientists identified distinct changes in the oral microbiome of patients with gastrointestinal tumors, according to study findings published in the journal Cell Host & Microbe.
The clinical investigation evaluated 507 individuals, comprising patients diagnosed with stomach cancer, colorectal cancer, metabolic conditions, and healthy volunteers. Researchers collected samples from each participant to compare the microbial communities present in saliva and stool.
To assess how closely mouth bacteria matched gut flora, the research team calculated a specialized mouth-gut index. Their evaluation showed that oral bacteria migrated into the digestive tract significantly more often in patients suffering from gastrointestinal cancer.
Oral bacteria and gastrointestinal cancer
This migration pattern was absent in participants with other health issues. Individuals diagnosed with diabetes, hypertension, or related metabolic disorders did not show the same shift of oral microbes into the gut ecosystem.
When evaluated as a diagnostic tool, a screening model relying exclusively on saliva bacteria analysis proved more accurate than several standard primary screening options for colorectal cancer that check for hidden blood in stool.
Colorectal cancer forms in the large intestine or rectum, while stomach cancer develops along the lining of the stomach. Early screening is crucial for successful treatment, but primary diagnostic tools like colonoscopies involve invasive endoscopic examination of the colon and require uncomfortable preparation routines.
Traditional non-invasive alternatives typically rely on fecal occult blood tests to detect unseen blood in stool samples, though these can produce inconsistent results. Yonsei University, a prominent research institution located in Seoul, South Korea, conducted the study to determine if saliva samples could offer a simpler diagnostic path.
Clinical limitations and next steps
Despite the promising results, the study authors emphasized that the saliva testing method cannot yet be deployed in clinical practice. Further studies are required before the approach can be introduced to doctors and hospital settings.
The authors noted that it remains unknown whether oral bacteria actively drive tumor development or if gastrointestinal tumors create an altered internal environment that allows mouth bacteria to spread through the gut.
The new research follows earlier findings in gastrointestinal health showing that frequent consumption of sugary drinks may increase the overall risk of developing stomach cancer.
