Pancreatic cancer is known as the 'silent killer' due to the difficulty of early detection. The prognosis is poor, with a 5-year survival rate of only about 10% after diagnosis.

However, a new study published in the Journal of the American Medical Association (JAMA) Oncology reveals that 27 types of bacteria and fungi living in the mouth increase the risk of pancreatic cancer by 3.5 times. This is noteworthy because thorough oral hygiene management could be a means to prevent one of the most deadly cancers.

Oral bacteria travel to the pancreas through saliva

It has long been known that people with poor oral health are more susceptible to pancreatic cancer. It has been revealed that when saliva is swallowed, oral bacteria travel to the pancreas, which plays an important role in digestion and blood sugar regulation. However, it was unclear which specific bacterial species were involved in this process.

This study, led by NYU Langone Health and the Perlmutter Cancer Center of the same university, analyzed the genetic information of microorganisms collected from the saliva of 122,000 healthy men and women and followed them for an average of about 9 years. During the study period, 445 individuals developed pancreatic cancer. Their oral microorganisms were compared with a control group of 445 individuals who did not develop cancer.


Bacteria causing periodontal disease also linked to pancreatic cancer

The results revealed that certain bacteria and fungi, particularly Candida strains that naturally exist on the skin and inside the body, are involved in increasing the risk of pancreatic cancer. The researchers found the same fungi in the tumor tissues of pancreatic cancer patients.

Additionally, bacteria causing severe periodontal disease (gum disease) such as Porphyromonas gingivalis (P. gingivalis), Eubacterium nodatum (E. nodatum), and Parvimonas micra (P. micra) were also found to be associated with an increased risk of pancreatic cancer.

Overall, the presence of 27 specific microorganisms together showed an effect of increasing the risk of developing pancreatic cancer by 3.5 times. Conversely, 8 types of oral bacteria were associated with a reduction in pancreatic cancer.

This suggests that maintaining the balance of oral microorganisms can play an important role in cancer suppression.

The oral microbiome, a diverse group of bacteria and fungi residing in the mouth, has been shown to affect health in various parts of the body and is being actively researched recently.

The same research team previously announced findings last year that specific oral bacteria are associated with an increased risk of head and neck squamous cell carcinoma (cancer occurring in the mouth and throat). In 2016, they only found clues that oral bacteria might be related to pancreatic cancer, but this study identified specific bacterial and fungal species for the first time.

Oral care as cancer prevention

This study is evaluated as the first large-scale analysis that elucidates the previously speculative link between oral health and pancreatic cancer at the level of specific bacterial and fungal species.

Pancreatic cancer is difficult to detect early, making it challenging to improve patient survival rates. Therefore, this discovery holds significant meaning as a potential early diagnostic tool.

Professor Ji-Young Ahn of NYU School of Medicine, who led the study, emphasized, “Analyzing the composition of bacteria and fungi in the mouth can preemptively identify people at high risk of pancreatic cancer.”


Small habits as a means to prevent deadly cancer

The researchers clarified that while they confirmed a correlation between oral microorganisms and pancreatic cancer, they did not prove a direct causal relationship. Nonetheless, this study shows that small habits that protect oral health can play an important role in preventing pancreatic cancer beyond simply protecting teeth.

Co-lead researcher Professor Richard Hayes emphasized, “Brushing and flossing are increasingly becoming evident as helpful not only in preventing gum disease but also in preventing cancer.”

The researchers stated that they plan to further explore how oral viruses affect cancer development and how the oral microbiome changes the survival rates of patients.

Related research paper address: DOI: 10.1001/jamaoncol.2025.3377

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