Periodontal Disease Linked to Increased Risk of Breast Cancer in Postmenopausal Women, Especially Smokers
A large prospective study of postmenopausal women investigating an association between periodontal disease and breast cancer risk has found that among all women in the study, the risk of breast cancer was 14% higher in women who had periodontal disease. Among women who had quit smoking within the past 20 years, those with periodontal disease had a 36% higher risk of breast cancer. Women who were smoking at the time of the study had a 32% higher risk if they had periodontal disease, but the association was not statistically significant. Those women who had never smoked and women who had quit more than 20 years ago had a 6% and 8% increased risk, respectively, if they had periodontal disease. Understanding a possible role of the oral microbiome in breast carcinogenesis could impact prevention, according to the results of this study by Freudenheim, which were published in Cancer Epidemiology, Biomarkers & Prevention.
Study Methodology
The researchers monitored 73,737 postmenopausal women enrolled in the Women’s Health Initiative Observational Study between 1994 and 1998. The women were between the ages of 50 and 79 and had no history of breast cancer. Study participants completed extensive self-administered questionnaires, physical examinations, and blood collection and were followed annually to ascertain additional exposure information and determine changes in health status.
History of periodontal disease diagnosis was determined on a questionnaire completed at year 5 of follow-up. Incident, primary, invasive breast tumors were verified by physician adjudication. Periodontal disease was by self-report. Hazard ratios (HRs) and 95% confidence intervals (CI) were estimated by Cox proportional hazards, adjusted for breast cancer risk factors. Because the oral microbiome of those with periodontal disease differs with smoking status, the researchers examined associations stratified by smoking.
Study Results
After a mean follow-up of 6.7 years, 2,124 women were diagnosed with breast cancer. Periodontal disease, reported by 26.1% of women, was associated with an increased breast cancer risk (HR = 1.14; 95% CI = 1.03–1.26), particularly among former smokers who quit within 20 years (HR = 1.36; 95% CI = 1.05–1.77). Among current smokers, the trend was similar (HR = 1.32; 95% CI = 0.83–2.11); there were few cases (n = 74) and the confidence interval included the null. The population attributable fraction was 12.06% (95% CI = 1.12–21.79) and 10.90% (95% CI = 10.31–28.94) for periodontal disease among former smokers quitting within 20 years and current smokers, respectively.
“We know that the bacteria in the mouths of current and former smokers who quit recently are different from those in the mouths of nonsmokers,” said Jo L. Freudenheim, PhD, Distinguished Professor in the Department of Epidemiology and Environmental Health at the University at Buffalo School of Public Health and Health Professions and first author of the study, in a statement. “One possible explanation for the link between periodontal disease and breast cancer is that those bacteria enter the body’s circulation and ultimately affect breast tissue. However, further studies are needed to establish a causal link.”
Dr. Freudenheim is the corresponding author of this study.
Funding for this study was provided by the National Heart, Lung, and Blood Institute, the National Institutes of Health, and the U.S. Department of Health and Human Services.
Robert J. Genco, PhD, DDS, reported receiving a commercial research grant from Sunstar; has received speakers bureau honoraria from Sunstar, Colgate Palmolive, Johnson & Johnson, Wrigley, Cigna Insurance Co., and Proctor and Gamble; and is a consultant/advisory board member for Sunstar. He is a member of the Scientific Advisory Panel of the American Academy of Periodontology, a nonfinancial interest which may be relevant to the submitted work. No potential conflicts of interest were disclosed by the other authors.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
