A large and growing body of research shows increased cancer risk is connected with periodontal disease.
Oral disease, chronic inflammation, and the oral microbiome are connected to cancers of the head and neck and throughout the body.
Human papillomavirus andFusobacterium nucleatumare two of the best understood oral microbes implicated in oropharyngeal cancer and colorectal cancer, respectively.
Oral microbes such asF. nucleatum, can travel from the mouth to other body sites and influence disease. Periodontal disease and inflammation can make this journey easier for the bacteria.
Add oral microbiome testing and improving your oral health to a list of cancer-mitigating actions you can take now.
Cancer is a leading global killer, taking an estimated10 million lives worldwide in 2020and diagnosed in over19 million new cases. In the US, 1 in 3 people will be diagnosed with cancer and about half of those people will die from it. Very likely you or someone you know has been affected by cancer.
You already know certain risk factors, likesmoking, lead to cancer. But did you know that a large, growing body of research is connecting poor oral health and a dysbiotic oral microbiome to cancers throughout the body?
Here we’ll take a close look at how gum disease may influence cancer and what members of the oral microbiome play a role in tumor development.
Gum disease and cancer
Many epidemiological studies over the years have reported associations between periodontal (gum) disease and cancer. Since half of adults in the US have periodontal disease, the public health impact could be huge if that relationship is causal. If so, you could potentially reduce the risk of developing cancer or slow it down by preventing or treating gum disease.
Overall cancer risk
Ameta-analysis of multiple studiesreported a14 - 20% increase in total cancer risk associated with gum disease, adjusting for smoking status — a major risk factor for both diseases.
Another large prospective cohort studyfollowed 7466 people, who underwent dental examinations and had no prior cancer history. Measuring probing depth and gingival recession — the same measures your dentist takes at your checkup — and tracking whether or not the participants developed cancer, researchers found thatsevere periodontal disease elevated overall cancer risk.
What is gum disease?
Periodontal (gum) disease is largely a chronic inflammatory disease driven by a pathogenic oral microbial community growing below the gum line. When we’re healthy, our immune systems can clear this microbial infection. Careful dental hygiene (flossing, water flossing, etc.) disrupts the surface biofilms that protect these bacteria, making it easier for your immune system to clear the rest.
During severe periodontal disease, the immune system responds erratically to the dysbiotic oral microbiome, producing chronic inflammation that can destroy bone and gum tissue, leading to bleeding and tooth loss. The oral pathogens persist, triggering a vicious cycle of chronic inflammation.
What causes cancer?
Driven by changes to genes (mutations or variants) that control the way our cells normally reproduce, cancer develops when some of our cells grow unchecked and then spread into surrounding tissues. Certain genetic variants enable these rogue cells’ aggressive growth and ability to escape our immune system checks on them.
Cancer can arise from:
Germline variants, or inherited mutations from our parents (i.e. theBRCA1andBRCA2variants in breast cancer). These variants are less common.
Somatic variants, or acquired mutations from DNA damage occurring over a person’s lifetime. Cancers arising from these mutations are more common. Cancerous mutations can be caused or accelerated by exposure to the following:
Since chronic inflammation and microbial infection are both hallmarks of periodontal disease, it isn’t surprising scientists and dentists are now paying closer attention to this possible connection.
Cancers in and around the mouth
Oral and oropharyngeal cancers most often occur on the tongue, tonsils, oropharynx, gums, roof and floor of the mouth, and the lips. The vast majority of oral and oropharyngeal cancers aresquamous cell carcinomas. Squamous cells are thin, flat cells that line the inside of our lips and oral cavity. Non-squamous cell types can also develop into cancer, but these are a mixed group of much rarer cancers.
Major risk factors include tobacco use, alcohol consumption, and advanced age. Ethanol and nicotine seem to be direct carcinogens. Age, of course, is associated with many risk factors: weaker immune response, accumulated mutations, long-term exposure to carcinogens, etc.
However, some people without these risk factors still develop oral and oropharyngeal cancers. What other factors might influence these cancers? Infectious microbes are other possible triggers.
It’s not just viruses; several studies of oral cancer samples summarizedherehave observed increases in certain species of oral bacteria, includingCapnocytophaga gingivalis,Prevotella spp.,Filofactor alocis, andFusobacterium spp.(which we'll discuss more later). However, it is still unclear if oral cancer itself shapes these microbiome changes or the other way around.
Periodontal disease also has a small but significantassociation to oral cancer, further signaling the need to prevent oral dysbiosis.
Cancers beyond the mouth
Periodontal disease itself or related dysbiotic oral microbiome shifts have been associated with other cancers, including:
It is important to note that although these studies suggest anassociationbetween periodontal disease or oral microbiome changes and cancer, they do not clearly indicate acausalrelationship and all the mechanisms driving cancer development are likely multifaceted and complex. Also, studies range widely in how they measure periodontal disease, and results can vary between different populations and places. Breast cancer, for example, shows only a low or moderate association with periodontal disease.
Despite the challenges and variation in these studies, gum disease consistently demonstrates association with a few cancers — one being colorectal cancer (CRC).
Since the mouth is the gateway to the rest of the body, especially the gastrointestinal system, it isn’t surprising to see associations between periodontal disease and cancers originating in the gut. Moreover, one oral bacterium,Fusobacterium nucleatum, is increasingly being implicated in colorectal cancer.
A strong connection between a common oral microbe and colorectal cancer
In a healthy mouth,F. nucleatumis a peaceful, common member of the oral microbiome – its numbers and potential to activate a strong inflammatory response kept in check.
However,F. nucleatumincreases rapidly in numbers during the early stages of periodontal disease,helping dental plaque growand organize by connecting early colonizers of the biofilm, likeStreptococcus spp., to anaerobic species associated with a dysbiotic microbial community, likePorphyromonas gingivalis. This ability, which allowsF. nucleatumto efficiently stick to other bacterial species in the dental plaque, alsoenables it to attach to and invade human host cells.
Now researchers understand more about how this bacterium, adapted for life in the oral cavity, influences disease in other body sites. More than just a passive microbial “passenger” along for the ride beyond the oral environment,F. nucleatumlikely drives tumor development in CRC.
Although a common oral species,F. nucleatumis found in only very low levels in a healthy gut. Many studies have observedF. nucleatumenriched in CRC tumors. From CRC tumor biopsies, researchers haveidentifiedoralF. nucleatumstrainswhile other researchers have evencultured liveF. nucleatum. Moreover, patients with high numbers ofF. nucleatumin CRC tissue faceworse prognosis.
Directly from the mouth to the gut. When we swallow 1.5 liters of saliva a day, we also ingest some oral microbes and give them direct access to the gut. Not all microbes are killed by the highly acidic conditions in the stomach and may end up lower in the GI tract.
Through the bloodstream(transient bacteremia). Normal activities, like brushing or flossing, and dental procedures can allow oral bacteria access to the circulatory system. If your gums are bleeding, that means microbes have a way into your bloodstream and other places in your body.
F. nucleatumhas even greater access to the bloodstream during periodontal disease, where gum tissue and bone are destroyed by inflammation and new paths to the circulatory system are created. Therefore, promoting a healthy, balanced oral microbiome may limit the ability of any oral bacteria to reach other body sites that may cause disease.
How you can lower your cancer risk
Although we cannot change our genetics, family history or aging, wecancontrol behaviors and exposures which may affect our risk for cancers associated with the oral microbiome.
Oral and oropharyngeal cancers are difficult to detect in early stages and there are currently no routine screening tests. However, dentists and dental hygienists are on the front lineslooking for early signs of oral cancer, like leukoplakia, lichen planus, or unhealing sores. Getting regular checkups by dentists and dental hygienists who are trained to look for these signs may help identify oral and oropharyngeal cancers in early stages – when treatment is most effective.
Since all colorectal cancers start as abnormal growths, or polyps, in the colon or rectum, routine screening tests starting at age 45 can find these polyps, allowing doctors to remove them before they become cancerous or prescribe treatment at an early stage of colorectal cancer. Such tests include colonoscopy and more recently, fecal immunochemical tests (FITs).
Although the HPV vaccine was originally developed to prevent cervical and other cancers related to the reproductive system, it also protects against oral infection by HPV types, especially HPV subtype 16, that cause oropharyngeal cancer. TheCDC recommendsroutine vaccination at 11 to 12 years old and for everyone up to age 26.
Make healthy choices
Periodontal disease, inflammation, and cancer share similar environmental risk factors. Reduce your risk by:
Avoiding or quitting tobacco
Limiting alcohol intake
Increasing physical activity
Eating nutrient-rich, whole foods
Pursuing diligent, regular oral hygiene
Maintaining or improving your oral health
In addition to routine dental checkups and cleanings, maintaining a healthy oral microbiome is vital to reducing your chances of developing oral diseases. You can learn a lot by understanding the ecosystem of bacteria that are living in your mouth.Send us a sample, and we'll analyze it for you. You'll get a complete report about your oral microbiome and what it means for the balance of your bacterial companions, what it means for your health, as well as personalized recommendations on how to use that knowledge to maximize your oral health!
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