Failing to floss may have consequences far worse than cavities, according to an international study led by Dominique Michaud, associate professor of epidemiology. The study, published Sept. 18 in the journal Gut, found a twofold increased risk of pancreatic cancer in patients with high levels of antibodies for an infectious oral bacterium.
A particularly insidious form of cancer, pancreatic cancer often remains symptomless until the tumor has spread, at which point patients typically have less than six months to live. Even with aggressive treatment, the disease has claimed the lives of notable figures including "The Last Lecture" author Randy Pausch '82 and Apple co-founder Steve Jobs.
Michaud's research shines light on a potential cause of pancreatic cancer - namely, oral health.
The study follows previous research that showed a correlation between gum disease and pancreatic cancer. Michaud and colleagues analyzed blood samples of approximately 800 volunteers from 23 centers across Europe in the European Prospective Investigation into Cancer and Nutrition cohort.
The first part of the study examined antibodies - factors made by the immune system to respond to specific threats - for five oral pathogens and found that subjects with high antibody levels for the gum disease-causing bacterium Porphyromonas gingivalis were twice as likely to have pancreatic cancer compared to matched controls.
Because the blood samples were obtained years before diagnosis, this relationship hints at a causal relationship between the bacteria and cancer in which the bacteria may actually promote cancer. Michaud has developed a "working hypothesis," theorizing that oral bacteria migrates to the pancreas via the blood or gut and causes "local damage" that can eventually become cancer.
The second part of the study looked at antibodies for naturally occurring oral bacteria. The researchers identified two subgroups, one of which had significantly higher antibody levels for the natural bacteria. This group had approximately half the risk of developing pancreatic cancer compared to their peers.
Michaud said the antibody levels for these natural bacteria may be indicative of immune strength. This may also explain why smoking is a risk factor, as it lowers antibody levels, she said.
Professor of Community Health Karl Kelsey, who was not involved in the study, described the study as having taken an "understudied and novel approach" in characterizing how the body's natural micro-organisms can contribute to cancer.
Michaud is taking a different approach in a follow-up study to understand the mechanisms by which bacteria can promote cancer. Using a technique called pyrosequencing, the study will examine pancreatic tumors for bacterial DNA. By comparing the results with oral bacterial data, it could demonstrate which bacteria can migrate from the mouth and promote cancer.
Michaud emphasized the importance of detecting the disease early. Though Michaud voiced concern about disparities in access to dental care, for her, the takeaway is simple. "People need to take care of their teeth," she said.