Oral bacteria could point toward cancer diagnosis: study
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Posted July 15, 2005 |
By Joe Hoyle Boston — Scientists from the Forsyth Institute have identified three species of oral bacteria whose elevated levels can be positively associated with increased incidence of oral squamous cell carcinoma, a discovery that could facilitate development of a saliva-based diagnostic test for this deadly form of cancer.
“Finding bacteria associated with oral squamous cell carcinoma encourages us to hope that we have discovered an early diagnostic marker for the disease,” said Dr. Donna Mager, assistant member of the staff in Forsyth’s Department of Periodontology and Molecular Genetics. “If future studies bear this out, it may be possible to save lives by conducting large-scale screenings using saliva samples.”
Nearly 30,000 Americans will be diagnosed with oral or pharyngeal cancer this year, according to the American Cancer Society. Ninety percent of oral cancer lesions are oral squamous cell carcinomas (OSCC), the Forsyth team noted, with a five-year survival rate of 54 percent despite advances in surgery, radiation and chemotherapy.
For their study, the Forsyth investigators collected unstimulated saliva samples from 229 cancer-free subjects and 45 subjects with OSCC and evaluated the samples for their content of 40 common oral bacteria using the checkerboard DNA-DNA hybridization method.
Of the 40 types of bacteria tested, three species — Capnocytophaga gingivalis, Prevotella melaninogenica and Streptococcus mitis — were elevated in the saliva samples from the subjects with OSCC. The investigators obtained similar findings when they controlled for gender, age and smoking history.
"Those results led us to hypothesize that the three species could serve as diagnostic indicators for OSCC,” Dr. Mager said. “And, in fact, we found that elevated salivary counts of the three bacteria correctly identified 80 percent of individuals with oral cancer and 83 percent of controls."
One possible explanation for the results is that oral cancer may change the oral ecology, allowing the three species of bacteria to colonize more rapidly, the investigators noted. However, they said the possibility that the bacteria may be causally associated with development of OSCC cannot be ruled out.
If the findings of the study can be replicated, the Forsyth team envisions development of a simple saliva test to diagnose OSCC administered in large screenings and analyzed by a diagnostic center with results returned within days.
But in the meantime, Dr. Mager noted she “cannot overemphasize" the importance of patients getting examined for signs of oral cancer at least once a year.
The findings of the Forsyth investigation are available online in the paper, “The salivary microbiota as a diagnostic indicator of oral cancer: A descriptive, non-randomized study of cancer-free and oral squamous cell carcinoma subjects,” published in the Journal of Translational Medicine.
The study was funded by the National Institute of Dental and Craniofacial Research and conducted in collaboration with the Dana Farber Cancer Institute and Massachusetts General Hospital.
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