Mouth bacteria test could detect and monitor oral and throat cancer

Bacteria in the mouth could be a tool for finding and monitoring oral and throat cancer, a first-of-its-kind study showed. Researchers at Johns Hopkins found that patients’ salivary microbiome is associated with head and neck squamous cell carcinoma—a finding that may lead to a saliva test for cancer biomarkers to provide earlier and more accurate diagnosis. Their study was published May 30, 2016 in the journal Oncotarget.

In particular, some of these biomarkers in saliva were associated with cancer due to human papilloma virus (HPV).

“One of the goals of our research is to better understand how the microbiome may influence the immune response to cancer and how the immune response affects the microbiome in turn,” said Rafael Guerrero-Preston, DrPH, MPH, Assistant Professor of Otolaryngology–Head and Neck Surgery at the Johns Hopkins University School of Medicine, in Baltimore, MD.

“Our findings suggest that we may one day use the composition of the microbiome to test for disease,” he explained.

For this study, the researchers obtained saliva samples from 42 patients—17 from patients with histopathologically-confirmed head and neck squamous cell carcinoma (HNSCC) and 25 from people with noncancerous epithelium to be used as controls. After patients with HNSCC underwent resection, the researchers sampled the subjects’ saliva again and then analyzed the samples to look for before-and-after differences.

The findings showed that patients with head and neck cancer had elevated levels of some bacteria and lower levels of others when compared with the controls. These results suggest that microbiota may be used as diagnostic and prognostic biomonitors for head and neck cancer, the researchers predicted.

Patients diagnosed with HNSCC, for instance, showed increased populations of Streptococcus, Dialister, and Veillonella, but decreased populations of Neisseria, Aggregatibacter, Haemophilus, and Leptotrichia when compared with control samples.

Samples from HNSCC patients also showed an increased prevalence of Lactobacillus at 9.1%, yet this genus was found in only 0.1% of noncancerous controls.

The findings also revealed correlations between certain bacteria and patients’ HPV status. Specifically, samples from HPV-positive patients showed increased Gemellaceae, Leuconostoc, and Veillonella when compared with HPV-negative samples. Veillonella, for example, was detected in 15% of HPV-positive samples but in only 9.4% of HPV-negative samples.

“We see some specific bacterial populations that are increased or lost in the presence of cancer when compared to healthy controls,” Dr. Guerrero-Preston summarized.

This may mean that either the tumor is affecting the microbiota in the mouth by killing bacteria that would fight cancer, or that these patients could be predisposed to cancer because they originally lacked bacteria that would prevent the tumor in the first place, he explained.

Further research will have to tease this out. Further studies are also needed to explain how specific microbiota affects immunotherapy, the researchers added.