Twenty-seven species of bacteria and fungi among the hundreds that live in people’s mouths have been collectively tied to a 3.5 times greater risk of developing pancreatic cancer, a US study shows.
Experts have long observed that those with poor oral health are more vulnerable to pancreatic cancer than those with healthier mouths. More recently, scientists have uncovered a mechanism that could help explain this connection, finding that bacteria can travel through swallowed saliva into the pancreas, an organ that helps with digestion. However, precisely which species may contribute to the condition had until now remained unclear.
Published in JAMA Oncology, the new analysis led by NYU Langone Health and its Perlmutter Cancer Center assessed the genetic make-up of microbes collected from the saliva of 122,000 healthy men and women.
For the study, the team assessed data from two ongoing investigations tracking Americans from across the country to better understand how diet, lifestyle, medical history, and many other factors are involved in cancer.
Shortly after enrolling, participants rinsed with mouthwash, providing saliva samples that preserved the numbers and species of microbes for testing. Researchers then followed up for roughly nine years on average to record any presence of tumours.
In the current study, the investigators analysed bacterial and fungal DNA from the spit samples. Then, they identified 445 patients who were diagnosed with pancreatic cancer and compared the DNA of their microbes with that of another 445 randomly selected study subjects who had remained cancer free.
The findings identified 24 species of bacteria and fungi that individually either raised or lowered pancreatic cancer risk. Another three kinds of bacteria tied to the cancer were already known to contribute to periodontal disease.
Altogether, the entire group of microbes boosted participants’ chances of developing the cancer by more than threefold.
In addition, by assessing the make-up of each participant’s oral microbiome, the scientists for the first time developed a tool that could estimate their cancer risk.
