A mouth rinse used to identify oral microbiome composition could serve as an early-detection tool for gastric cancer, new evidence suggests.

Researchers found distinct bacterial composition differences in patient samples that point to the potential for oral microbial signatures to be used as biomarkers for assessing gastric cancer risk.

“Too many patients are being diagnosed too late. There are no formal screening guidelines for gastric cancer, and more than half of patients with gastric cancer do not receive a diagnosis until their cancer is already at an advanced stage,” said Shruthi Reddy Perati, MD, a general surgery resident at Rutgers University Robert Wood Johnson School of Medicine in New Brunswick, New Jersey.

Detecting gastric cancer now generally requires an invasive procedure, such as endoscopy. Therefore, a noninvasive “swish and spit” test could be more accessible and allow for more widespread screening, Perati said at a May 8 press briefing during which her research (Abstract 949) was previewed for Digestive Disease Week (DDW) 2024.

Gastric cancer, also known as stomach cancer, is the fourth most common cause of cancer-related death in the world. The United States can expect 26,890 new cases and 10,880 deaths from this type of cancer in 2024, the American Cancer Society estimates.

Microbial Signatures Found

Perati and colleagues collected oral rinse samples from 98 patients: 30 known to have gastric cancer , 30 with precancerous gastric conditions (pre–gastric cancer), and 38 control participants without pre-gastric or gastric cancer. Sixty-two percent were women, 32% were Hispanic, 31% had diabetes, and 18% were smokers.

The researchers analyzed the samples for alpha and beta diversity and conducted differential analysis using the framework called analysis of compositions of microbiomes.

They found distinct differences between the oral microbiomes of the healthy group and those of the groups with gastric cancer and pre–gastric cancer. In addition, the microbiomes of participants with cancer and of those with precancerous conditions were similar.

The results suggest that the microbiome changes may occur as soon as the stomach environment starts to undergo changes that can eventually turn into cancer.

“The oral microbiome may serve as a window into the composition of the stomach environment,” Perati said.

The investigators created a screening model to detect the most relevant 13 bacterial genera that differed between the control group and the gastric cancer and pre–gastric cancer groups. The tenfold cross-validation model demonstrated good ability to discriminate using bacteria alone (area under the curve [AUC], 0.74) and was further improved with the addition of clinical variables, including demographics and comorbidities (AUC, 0.91), the researchers noted.

Additional Considerations

The microbiome can vary between people and within the same individual over time. Probiotics, antibiotics, and diet can lead to changes in the microbiome, Perati said.

When asked how these changes could affect the accuracy of an oral rinse test, Perati said “it’s known that, in general, dietary modifications can have an impact on the diversity and the prevalence of certain bacteria throughout the GI tract.”

Though variance is expected, we’re hoping to see that the differences in the microbiome composition between the malignant groups and the control groups are more significant than those lower-level background changes due to dietary modifications, for example, she added.

The research is in its early days, and the results need to be validated in a larger study, Perati said.

Still, the study “has huge implications that could eventually lead to the development of noninvasive and accessible early screening for gastric cancer,” she said.

Perati reported no relevant financial relationships. The study was independently supported. 

Damian McNamara is a staffjournalist based in Miami. He covers a wide range of medical specialties, including infectious diseases, gastroenterology and critical care. Follow Damian on X/Twitter: @MedReporter.