Mouthwash microbiome test shows promise for detecting GI cancers

A simple mouthwash could one day help detect stomach and colorectal cancers early, without invasive procedures. Researchers at Yonsei University in Seoul, South Korea, found that the bacterial ecosystems in the mouth carry a distinctive signature of these cancers. Their study, published in Cell Host & Microbe, analyzed paired saliva and stool samples from 507 volunteers—including healthy individuals, people with metabolic disorders, and patients with gastric or colorectal cancer—using genetic sequencing. The team developed a 'mouth-to-feces' (MF) index that tracks identical bacterial genetic variants in both the mouth and gut, and found this index was significantly elevated in cancer patients but not in those with metabolic conditions. The association held even after adjusting for alcohol consumption, body mass index, and exercise Source: ABC.es, Infobae.

Key findings

• The MF index was markedly higher in patients with stomach and colon cancer, but not in those with type 2 diabetes, hypertension, or hyperlipidemia Source: ABC.es.
• When compared with the standard fecal occult blood test for colorectal cancer screening, the oral rinse sample showed superior sensitivity in identifying cancer patients Source: ABC.es, Infobae.
• The signal could be detected using only oral samples, which surprised researchers: "It is remarkable that cancer information can be recovered from oral samples alone" Source: ABC.es.

What's next

The team plans a prospective validation study in undiagnosed individuals and will use higher-resolution metagenomic sequencing. They will also investigate causality—whether increased microbial exchange contributes to cancer development or whether cancer creates conditions that allow oral bacteria to persist in the gut Source: Infobae. Before clinical use, further studies in real screening populations are needed, said researcher Tae Il Kim Source: Infobae.