Oral Bacteria Linked With Stomach Cancer

Richard Gawel
Photo by Derren Ready, Wellcome Images

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Photo by Derren Ready, Wellcome Images

Elevated pathogen colonization and a lack of bacterial diversity in the mouth were identified in people with precancerous lesions that could precede stomach cancer, according to research by the New York University (NYU) College of Dentistry and the NYU School of Medicine. These findings provide new evidence that the increase in pathogens associated with periodontal disease could contribute to the development of precancerous lesions of stomach cancer. 

“Our study reinforces earlier findings that poor oral health is associated with an increased risk of precancerous lesions of stomach cancer,” said Yihong Li, DDS, MPH, DrPH, professor of basic science and craniofacial biology at NYU Dentistry and the study’s corresponding author.

The American Cancer Society estimated that 26,370 new cases of stomach or gastric cancer would be diagnosed in 2016, resulting in 10,703 deaths. Accumulating evidence suggests that chronic inflammation caused by oral bacterial infections may contribute to the development and progression of various types of cancer, including stomach cancer.

Although risk factors such as Helicobacter pylori colonization, cigarette smoking, and a diet including salt and preserved foods have been confirmed to contribute to the development of stomach cancer, many new cases unrelated to these risk factors are diagnosed each year. Scientists have hypothesized that a group of pathogens may be responsible for causing periodontal disease and the resulting chronic systemic inflammation that may contribute to the development of gastric cancer. 

The NYU study assessed the association between periodontal pathogen colonization and the potential risk of developing precancerous lesions, including chronic atrophic gastritis, intestinal metaplasia, and dysplasia, that may predict stomach cancer. It included 105 individuals scheduled to receive an upper endoscopy. 

After the endoscopic procedure and histopathologic evaluation, 35 people were diagnosed with precancerous lesions of gastric cancer. Another 70 people of the same ages without precancerous lesions were included in the study control group.

The researchers performed full-mouth examinations to examine the subjects’ periodontal conditions. They also collected saliva and dental plaque samples to evaluate colonization by several pathogens, including Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, and Aggregatibacter actinomycetemcomitans, and to characterize oral microbial diversity.

Compared with the control group, patients with precancerous lesions experienced higher prevalence of bleeding when probed (31.5% versus 22.4%), higher levels of two pathogens (T denticola and A actinomycetemcomitans), and less bacterial diversity in their saliva.

Further analysis accounting for sociodemographic factors, oral health behaviors, and periodontal assessments revealed additional predictors of precancerous lesions: elevated colonization of T forshythia, T denticola, and A actinomcetemcomitans, decreased bacterial diversity in dental plaque, and not flossing regularly. 

The researchers concluded that the colonization of periodontal pathogens and the alternated bacterial diversity in the oral cavity are important factors that, when at higher or lower levels respectively, may contribute to an increased risk of developing precancerous gastric lesions. 

“Based on our findings, treatment of chronic periodontal disease and control of periodontal pathogen infections should be included in future strategies for preventing stomach cancer,” said Li. 

The study, “Chronic Periodontal Disease, Periodontal Pathogen Colonization, and Increased Risk of Precancerous Gastric Lesions,” was published by the Journal of Periodontology.

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