Patients suffering from oral cancer have increased levels of certain bacteria in their saliva

Jul 6 2005

Patients suffering from oral cancer have increased levels of certain bacteria in their saliva, according to new research published today in the Open Access journal, Journal of Translational Medicine.

Six common species of bacteria were found at significantly higher levels in the saliva of patients with oral squamous cell carcinoma (OSCC) than in the saliva of healthy individuals. The researchers were able to use three of the six species as a diagnostic tool to predict more than 80% of oral cancer cases. These preliminary findings indicate that three species of bacteria may be incidentally or causally linked with OSCC, and if so detection of these species could be used as a simple, rapid and non-invasive saliva-test to diagnose oral cancer.

Previous studies have reported that certain common oral bacteria are often found on or in oral cancer lesions. Though previous research has reported that the microbiota of OSCC lesions differs from that found on the soft tissues of cancer-free individuals, little is known about the salivary microbiota of oral cancer patients. Currently, studies are examining whether bacteria may be incidentally or causally associated with oral cancer and if so, whether these species may be used as markers for oral cancer.

In order to determine if the salivary microbiota in patients with OSCC would differ from that found in oral cancer-free individuals, Donna Mager and colleagues, from the Forsyth Institute and the Dana Farber Cancer Institute in Boston, United States, collected saliva samples from 45 individuals diagnosed with OSCC and 229 controls. A computer then matched a subset of 45 members of the control group for age, gender and smoking with the 45 OSCC subjects. The saliva samples were then individually analysed for their content of forty bacterial species using bacterial DNA probes.

Comparisons between controls and the 45 OSCC patients showed that six common bacteria - Prevotella melaninogenica, Capnocytophaga gingivalis, Capnocytophaga ochracea, Eubacterium saburreum, Leptotrichia buccalis and Streptococcus mitis - were found at significantly higher levels in OSCC patients compared with the controls. Three of these species of bacteria, C. gingivalis, P. melaninogenica and S. mitis, when used as diagnostic indicators of oral cancer, were found to correctly predict more than 80% of oral cancer cases.

OSCC accounts for 90% of all oral cancers. The five-year survival rate for this form of cancer - 54% - is amongst the lowest of the major cancers. Of the 400,000 new cases diagnosed each year worldwide, the disease kills one person every hour - more people than cancers of the cervix, brain, ovary, liver, kidney, malignant melanomas or Hodgkin's lymphoma. Currently the best method of detecting oral cancer is an annual examination of the mouth, head and neck. So far however, general population screening has not been shown to reduce the incidence or mortality of oral cancer, and so there is a demand for an inexpensive, noninvasive and easy-to-use diagnostic test for oral cancer. These findings could form the basis of the development of a straightforward saliva test for the diagnosis of oral cancer. If oral cancer is detected in its early stages, five-year survival rates dramatically improve to 80 - 90%.