NEW ORLEANS — The presence of two species of bacteria linked to periodontal disease in the mouths of healthy individuals was associated with an increased risk of subsequently developing pancreatic cancer, according to research presented here at the AACR Annual Meeting 2016, April 16-20.
“Previous studies have shown that indicators of poor oral health, including a history of periodontal disease and lots of missing teeth, are associated with an increased risk of pancreatic cancer,” said Jiyoung Ahn, PhD, associate professor of population health and associate director of population sciences at the Laura and Isaac Perlmutter Cancer Center at NYU Langone Medical Center in New York. “To test the idea that this association is driven by species of oral bacteria linked to periodontal disease, we first needed to determine whether these bacteria are even associated with pancreatic cancer risk.
“We found that Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, two species of bacteria linked to periodontal disease, were associated with a more than 50 percent increased risk of pancreatic cancer,” Ahn continued. “These data do not show a causal relationship, but they are the first steps in understanding a potential new risk factor for pancreatic cancer, which is vital if we are to develop new approaches for pancreatic cancer prevention and early detection in the future.”
Ahn, Xiaozhou Fan, a graduate student working in Ahn’s laboratory, and colleagues conducted a nested case-control study using samples and data from the Cancer Prevention Study II and the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial cohorts. Both these cohorts enrolled healthy people and followed them over a long period for a variety of outcomes, including development of cancer.
The researchers analyzed oral wash samples collected at study enrollment from 361 people who later went on to develop pancreatic cancer and from 371 matched controls. They used genomic technologies to generate a profile of the bacterial species present in each sample and performed logistic regression analysis to study the association between individual species of bacteria and risk of pancreatic cancer, controlling for other risk factors, including age, smoking status, and body mass index.
The presence of P. gingivalis in oral wash samples was associated with a 59 percent increased risk for pancreatic cancer and the presence of A. actinomycetemcomitans was associated with a 119 percent increased risk. Risks remained even after excluding samples from people who developed pancreatic cancer within two years of collection of their oral wash samples, which increased the research team’s confidence in the associations that were identified, according to Ahn.
“About 1.5 percent of U.S. men and women will be diagnosed with pancreatic cancer at some point in their life,” explained Ahn. “However, only 5 percent survive five years or more after their diagnosis. New approaches to pancreatic cancer prevention and early detection are urgently needed. Although our new findings cannot be directly translated into such approaches, if they are confirmed in additional studies, they could point to new ways to screen for the disease, and if the associations are found to be causal, they could point to potential prevention approaches.”
According to Ahn, a major limitation of the study was that the population studied was not very diverse—it was predominantly non-Hispanic white and healthy—so the results might not be generalizable to the whole population.
This study was funded by the National Cancer Institute. Ahn and Fan declare no conflicts of interest.