Oral microbiome linked to pancreatic cancer risk, study finds

A study led by researchers at NYU School of Medicine and published in JAMA Oncology found that certain bacteria and a yeast living in the mouth are associated with an increased risk of pancreatic cancer. In the largest analysis of its kind, scientists tracked 900 American participants over roughly nine years, comparing saliva microbiomes from 445 patients who developed pancreatic cancer with 445 randomly selected cancer-free individuals. The study suggests that harmful microbes from the mouth can travel via saliva to the pancreas and may triple the risk for some people, though investigators emphasize that the findings show a correlation rather than a proven cause-and-effect relationship.

In the study, researchers identified 24 species of bacteria and fungi that either raised or lowered pancreatic cancer risk after accounting for factors such as smoking, age and race. Among the microbes linked to the cancer were three bacteria already known to contribute to periodontal disease, a gum infection that can damage bone and soft tissue around the teeth. The team also found that a type of yeast, candida, which commonly lives on skin and mucous membranes, may play a role in pancreatic cancer. At baseline, participants rinsed with mouthwash and provided saliva samples, and researchers then followed them for about nine years to record cancer diagnoses.

By analyzing the bacterial and fungal DNA in saliva from the cancer patients and the cancer-free controls, the researchers concluded that the entire group of harmful microbes was associated with more than a threefold increase in pancreatic cancer risk. Lead author Yixuan Meng, PhD, said the findings offer new insight into the relationship between the oral microbiome and pancreatic cancer. The team stressed that the work does not establish a direct cause-and-effect link, but rather a correlation that could help guide future screening strategies.

Ahn, study co-author and professor, said that profiling the mouth’s bacterial and fungal populations could help oncologists identify individuals who might benefit from targeted pancreatic cancer screening. By characterizing a patient’s oral microbiome, clinicians could potentially flag those at higher risk and tailor surveillance accordingly. Yet the researchers cautioned that more work is required to confirm whether these microbes contribute to cancer development or merely accompany other risk factors.

Pancreatic cancer remains one of the most lethal forms of cancer and cases are rising in some populations. In the report, researchers note that pancreatic cancer kills just over 10,000 people each year in the United States and the United Kingdom, roughly one death per hour, with projections indicating a record high of about 201,000 cases worldwide by 2040. When detected early, about half of patients survive at least a year; once the disease has spread, only about one in ten survive beyond that point. Cancer Research UK has previously estimated that about 22 percent of cases are linked to smoking and about 12 percent to obesity. Some analyses have discussed shifts in incidence among younger people in certain regions, though the overall numbers remain small relative to older age groups. Symptoms that can accompany pancreatic cancer include jaundice, itching, darker urine, loss of appetite, unintended weight loss and abdominal bloating. Because these signs overlap with many other conditions, medical evaluation is important if they persist for more than four weeks.

The pancreas, a tadpole-shaped organ behind the stomach, plays a key role in digestion and hormone regulation. It measures about 25 centimeters in length, producing enzymes that help break down food. The researchers said their findings warrant further study into how the mouth’s microbiome may influence prognosis and whether oral viruses might contribute to cancer risk, as well as whether maintaining good oral hygiene could indirectly affect pancreatic cancer outcomes. The team plans to extend their work to examine whether oral infections beyond bacteria and fungi, such as viruses, are associated with cancer risk and how the mouth’s microbial landscape might influence a patient’s trajectory after diagnosis.