Research points to associations between periodontal pathogens and colorectal cancer

A recent study shows evidence that there is an association between the periodontal pathogen, Fusobacterium nucleatum, and colorectal cancer, but many questions still remain. Dr. Richard Nagelberg explains what is and is not known about the research findings at this time, and discusses the scientific studies this could lead to in the future.

A common periodontal pathogen, Fusobacterium nucleatum (F. nucleatum), is the subject of research regarding its association with colorectal cancer (CRC). This research—published in the peer-reviewed medical journal, Carcinogenesis—demonstrates that F. nucleatum can be seeded in the gastrointestinal tract, specifically the large intestine, where it is highly associated with CRC. (1)

The study raised some interesting possibilities, such as the potential use of F. nucleatum for the early detection of CRC. It also indicated that additional Fusobacterium species are also associated with CRC, including Fusobacteriumperiodonticum, among others. An intriguing finding is that treatment with metronidazole decreases the aggressiveness of this type of cancer.

At this time, there are a number of unknowns regarding the research findings. It is not known whether the mouth is the primary source of F. nucleatum to seed the gut. It is known, however, that F. nucleatum is associated with the primary tumor and metastatic sites.

It bears emphasizing that the studies undertaken to date have demonstrated an association between Fusobacterium and colorectal cancer, but many questions remain. There is evidence that Fusobacterium is a passenger bacterium or that it promotes cancer progression rather than plays a causative role. These are among the details that need to be sorted out. Additional studies likely will try to determine if other bacteria are also involved and if the reduction in Fusobacterium has an impact on CRC incidence, severity, etc.

One of the primary questions that needs to be answered is how the source of the Fusobacterium finds its way to the gut. This should be identifiable by comparing the DNA of oral sources of Fusobacterium with bacteria found in stool samples. Further studies may seek to determine whether Fusobacterium is also associated with Clostridium difficile (C. difficile or C. diff.), irritable bowel syndrome (IBS), or Crohn’s disease.

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As is the case with any study demonstrating a link between the mouth and the body, a significant amount of research with consistent conclusions needs to be in place before it translates into modifications in the delivery of care. It is not, however, too soon to put more horsepower into our efforts to educate patients about the need for meticulous bacterial reduction on a daily basis and recommend the products that will maximize those efforts. It’s worth it for the health of the mouth, and it may have positive downstream effects as well.

Reference

1. Amitay EL, Werner S, Vital M, et al. Fusobacterium and colorectal cancer: causal factor or passenger? Results from a large colorectal cancer screening study. Carcinogenesis. 2017;38(8):781-788. doi: 10.1093/carcin/bgx053.

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