Mouth Bacteria Linked To Colorectal Cancer, Study Shows

If colorectal cancer is found at an advanced stage (or if it recurs after being removed) it can be difficult to treat. Young people are also becoming more likely to develop the disease - often in an advanced form - and it's not known why.

But new research about colorectal cancer may help uncover answers: a recent study has linked colorectal cancer to a bacteria that's associated with gingivitis in the mouth.

"Scientists found a subtype of bacteria, called fusobacterium nucleatum, in the colon next to a tumor," says Philip Philip, M.D., Ph.D., a medical oncologist at Henry Ford Health who specializes in gastrointestinal cancers. "Just because bacteria are sitting next to a tumor doesn't mean they caused that tumor to develop. But upon further investigation, scientists confirmed there's a reasonable chance F. nucleatum may have caused colorectal cancer in the patients they studied."

How Our Microbiome Is Linked To Our Health

Trillions of bacteria live on us and in us. Each area of the body has its own network of bacteria, otherwise known as a microbiome. Diverse, flourishing microbiomes help protect us from digestive issues, skin conditions and illnesses - both physical and mental. But unhealthy microbiomes (or microbiomes that have a predominant overgrowth of one type of bacteria) may contribute to the development of illness.

"Think of each microbiome as a family of bacteria," says Dr. Philip. "The microbiome in the mouth, for example, has unique features that are different from bacteria in other areas of the body. And within that family, some members are more problematic - like F. nucleatum, which grow and flourish in environments with poor oral hygiene, dental plaque and gingivitis. And now we know they may also contribute to the development of colorectal cancer."

It's not yet known why F. nucleatum may cause colorectal cancer, but Dr. Philip has a few theories.

"These bacteria should not be able to survive the trip to the colon," he says. "Before they get to the colon, they have to go through the stomach, which tries to sterilize its contents. If F. nucleatum make it to the colon, there might be an issue with the sterilizing process, which could lead to illness."

Or, he explains, these bacteria may have developed a way to survive this environment - which is the more likely reason they are related to cancer.

Future Colorectal Cancer Screening & Treatment Methods

If F. nucleatum causes colorectal cancer, can preventing it be as easy as practicing proper oral hygiene? While Dr. Philip says we can't say for sure, it's definitely part of maintaining a healthy lifestyle. Think: limiting sugar and processed foods, flossing and thoroughly brushing your teeth - along with biannual trips to the dentist for cleanings and checkups.

Other, well-established lifestyle risk factors for colorectal cancer include having obesity, smoking and drinking alcohol. "Even with this knowledge, however, we can't exactly pinpoint what causes colorectal cancer in a given patient - and we cannot explain why people are getting it at younger ages," says Dr. Philip. "But knowing this association between mouth bacteria and colorectal cancer may help us develop better screening, treatment and prevention methods.

"For example, instead of (or in addition to) colonoscopy, a mouth swab for F. nucleatum may help detect colorectal cancer before it starts. If we test ten people and find that two of them have these bacteria, we could mark them as high risk and put them under close surveillance, perform colonoscopy earlier - or even develop a vaccine against these bacteria to prevent them from developing colorectal cancer."

Vaccines for cancer prevention are not new: the HPV vaccine, for example, helps to prevent someone from contracting the virus that causes cervical, vaginal, vulvar, throat, penile and anal cancers.

"New screening and treatment methods for colorectal cancer require additional studies to understand more about the biology of this bacteria, but it's very interesting and promising," says Dr. Philip. "Not least of all because knowing that bacteria may cause colorectal cancer could help us find similar causes for other cancers. Whatever discoveries we make in one cancer help us make strides in other cancers."

Reviewed by Philip A. Philip, M.D., Ph.D., F.R.C.P., an internationally renowned medical oncologist specializing in gastrointestinal cancers. He has led numerous studies in the areas of gastrointestinal tumors. He is the director of gastrointestinal oncology, co-director of the Pancreatic Cancer Center and medical director of research and clinical care integration at Henry Ford Health - Cancer. He sees patients at Henry Ford Cancer in Detroit and Henry Ford Medical Center - Columbus.