January 23, 2018
Severe gum disease not only may increase the risk for cancer, including lung and colorectal cancer but also may increase the likelihood of dying of the disease, particularly pancreatic cancer, suggest results from two large-scale studies from the United States and from Finland.
The US study, led by Dominique Michaud, ScD, professor of public health and community medicine at Tufts University School of Medicine, Boston, Massachusetts, included almost 7500 individuals who had undergone dental examination. Of them, over 1600 developed cancer.
The findings, which were published online in the Journal of the National Cancer Institute on January 12, showed that severe periodontitis was associated with a 24% increased risk for cancer, with the highest risks seen for lung cancer and colorectal cancer.
"This is the largest study addressing the association of gum disease and cancer risk using dental examinations to measure gum disease prior to cancer diagnosis," Dr Michaud said in a statement.
"Additional research is needed to evaluate if periodontal disease prevention and treatment could help alleviate the incidence of cancer and reduce the number of deaths due to certain types of cancer," he added.
While also acknowledging the need for more work on, for example, the racial disparities they identified in the study, the team believe that the findings underline the need for expanded access to dental insurance.
Study coauthor Elizabeth Platz, ScD, from Johns Hopkins Bloomberg School of Public Health and the Johns Hopkins Kimmel Cancer Center, Baltimore, Maryland, said, "Knowing more about the risks that come about with periodontal disease might give more support to having dental insurance in the way that we should be offering health insurance to everyone."
In the second study, Timo Sorsa, DDs, PhD, from the University of Helsinki and Helsinki University Central Hospital, Finland, and colleagues examined registry data on over 68,000 adults who had made a primary dental healthcare visit.
This revealed that periodontitis was associated with a 33% increased risk for overall cancer mortality. The mortality risk associated with gum disease among individuals with pancreatic cancer was far higher, with a more than twofold increased risk.
The study was published in the International Journal of Cancer on January 11.
Dr Sorsa and colleagues also refer to another study they conducted, recently published in the British Journal of Cancer, which shows that a virulence factor associated with a bacterium seen in periodontitis also occurs in gastrointestinal tumors.
"These studies have demonstrated for the first time that the virulence factors of the central pathogenic bacteria underlying gum disease are able to spread from the mouth to other parts of the body, most likely in conjunction with the bacteria, and take part in central mechanisms of tissue destruction related to cancer," said Dr Sorsa in a statement.
Consequently, the prevention and early diagnosis of periodontitis could be important for not only oral health but overall well-being.
"In the long run, this would be extremely cost-effective for society," said Dr Sorsa.
Largest Study Based on Dental Exam
To date, most studies looking at the association between periodontitis and cancer risk have relied on self-reports. In contrast, the study conducted by Dr Michaud and colleagues included a dental examination.
The team used data from the Atherosclerosis Risk in Communities study cohort, a prospective analysis of 15,792 individuals aged 44 to 66 years who were recruited from four areas of the United States between 1987 and 1989.
All the participants took part in a baseline examination, followed by three follow-up visits over 10 years. At the fourth visit, the remaining participants were invited to undergo a clinical dental examination that probed depth and gingival recession at six sites.
Via linkage to state cancer registries, supplemented by medical records and hospital discharge codes, the team assessed the cancer incidence between 1987 and 2012, while cancer deaths were obtained from death certificates.
Ruling out participants with a cancer history, the team included in the current analysis 6056 individuals who underwent the dental examination and 1410 who had no teeth (that is, were edentulous).
Depending on the definition used, 2420 to 2543 individuals had no or mild periodontitis, while 2104 to 2514 had moderate periodontitis, and 1122 to 1409 had severe periodontitis.
More severe periodontitis, regardless of the definition of severity used, was associated with being older, male, black, less educated, obese, and a smoker.
During a mean follow-up of 14.7 years, there were 1648 incident cancers and 547 cancer deaths in the study population.
Compared with individuals who had no or mild periodontitis, those who had severe periodontitis (defined as >30% of sites with attachment loss >3 mm) had a significantly increased risk for total cancer, at a hazard ratio of 1.24 (P = .004).
A similar association was observed between edentulism and total cancer risk; the hazard ratio compared with no or mild periodontitis was 1.28.
The association between severe periodontitis and cancer risk was particularly strong for lung cancer, at a hazard ratio of 2.33 (P < .001) vs no or mild periodontitis, even after taking into account cigarette smoking status and pack-years of smoking.
However, the association was present only in white individuals and was stronger in men than women.
When the team looked at colorectal cancer, they found that edentulism was associated with a significant 80% increased risk, while severe periodontitis was associated with a 50% increased risk. Among never-smokers, the risk for colorectal cancer was increased more than twofold and was present in both white and black participants.
Link to Pancreatic Cancer
In the Finnish study, Dr Sorsa and colleagues used the patient register from Helsinki's Public Dental Service to identify individuals aged 29 years or older who had made at least one primary dental healthcare visit in 2001 or 2002.
These were linked to the register of deaths from Statistics Finland, which provided information on both the date and case of death. In addition, socioeconomic and education data were obtained, and drug prescriptions were collated, alongside cancer diagnosis data from the Finnish Cancer Registry.
The researchers included 68,273 patients, yielding 664,020 person-years over a median follow-up of 10.1 years. The mean age at baseline was 43 years, and 58% of patients were female.
The most common dental procedure was endodontic treatment, in 70.3% of patients, followed by treatment for gingivitis in 40.6% of patients and periodontitis treatment in 20.5%.
During follow-up, there were 797 cancer deaths, of which 199 (25%) were in patients with periodontitis, for a crude cancer mortality rate of 14.45 per 10,000 person-years.
In comparison, the crude cancer mortality rate among individuals without periodontitis was 11.36 per 10,000 person-years.
The most common diagnosis in patients who died of cancer was lung cancer, at a crude mortality rate of 2.42 per 10,000 person-years, followed by breast cancer (1.89 per 10,000 person-years), pancreatic cancer (1.13 per 10,000 person-years), and prostate cancer (0.95 per 10,000 person-years).
Further analysis showed that after adjustment, periodontitis was associated with a significantly increased risk for both overall and pancreatic cancer mortality, at mortality rate ratios of 1.33 and 2.32, respectively.
Michaud and colleagues' study was supported by awards from the National Cancer Institute of the National Institutes of Health. The Atherosclerosis Risk in Communities study was supported by awards from the National Heart, Lung, and Blood Institute of the National Institutes of Health. Sorsa and colleagues' study was supported by grants from the Finnish Women Dental Society and the Helsinki University Tulevaisuusrahasto, the Helsinki University Hospital Research Foundation, Helsinki, Finland, and the Karolinska Institutet, Stockholm, Sweden. No authors have disclosed any relevant financial relationships.