Bacteria may signal pancreatic cancer risk

A new study finds significant associations between antibodies for multiple oral bacteria and the risk of pancreatic cancer, adding support for the emerging idea that the ostensibly distant medical conditions are related.

The study of blood samples from more than 800 European adults, published in the journal Gut, found that high antibody levels for one of the more infectious periodontal bacterium strains of Porphyromonas gingivalis were associated with a two-fold risk for pancreatic cancer. Meanwhile, study subjects with high levels of antibodies for some kinds of harmless “commensal” oral bacteria were associated with a 45-percent lower risk of pancreatic cancer.

“The relative increase in risk from smoking is not much bigger than two,” said Brown University epidemiologist Dominique Michaud, the paper’s corresponding author. “If this is a real effect size of two, then potential impact of this finding is really significant.”

Pancreatic cancer, which is difficult to detect and kills most patients within six months of diagnosis, is responsible for 40,000 deaths a year in the United States.

Several researchers, including Michaud, have found previous links between periodontal disease and pancreatic cancer. The Gut paper is the first study to test whether antibodies for oral bacteria are indicators of pancreatic cancer risk and the first study to associate the immune response to commensal bacteria with pancreatic cancer risk. The physiological mechanism linking oral bacteria and pancreatic cancer remains unknown, but the study strengthens the suggestion that there is one.

“This is not an established risk factor,” said Michaud, who is also co-lead author with Jacques Izard, of the Forsyth Institute and Harvard University. “But I feel more confident that there is something going on. It’s something we need to understand better.”

Pancreatic cancer is highly lethal and difficult to detect early. In a new study, researchers report that people who had high levels of antibodies for an infectious oral bacterium turned out to have double the risk for developing the cancer. High antibody levels for harmless oral bacteria, meanwhile, predicted a reduced pancreatic cancer risk.

Izard, a microbiologist, said the importance of bacteria in cancer is growing. “The impact of immune defense against both commensals and pathogenic bacteria undeniably plays a role,” he said. “We need to further investigate the importance of bacteria in pancreatic cancer beyond the associated risk.”

Prospective, controlled study

To conduct their research, Michaud and Izard drew on medical records and preserved blood samples collected by the Imperial College-led European Prospective Investigation into Cancer and Nutrition Study, a massive dataset of more than 500,000 adults in 10 countries. Detailed health histories and blood samples are available from more than 380,000 of the participants.