Faculty Bibliography

Individual bacteria and shifts in the composition of the microbiome have been associated with human diseases including cancer. To investigate changes in the microbiome associated with oral cancers, we profiled cancers and anatomically matched contralateral normal tissue from the same patient by sequencing 16S rDNA hypervariable region amplicons. In cancer samples from both a discovery and a subsequent confirmation cohort, abundance of Firmicutes (especially Streptococcus) and Actinobacteria (especially Rothia) was significantly decreased relative to contralateral normal samples from the same patient. Significant decreases in abundance of these phyla were observed for pre-cancers, but not when comparing samples from contralateral sites (tongue and floor of mouth) from healthy individuals. Weighted UniFrac principal coordinates analysis based on 12 taxa separated most cancers from other samples with greatest separation of node positive cases. These studies begin to develop a framework for exploiting the oral microbiome for monitoring oral cancer development, progression and recurrence.

BACKGROUND: The early detection and excision of potentially malignant disorders (PMD) of the lip and oral cavity that require intervention may reduce malignant transformations (though will not totally eliminate malignancy occurring), or if malignancy is detected during surveillance, there is some evidence that appropriate treatment may improve survival rates. OBJECTIVES: To estimate the diagnostic accuracy of conventional oral examination (COE), vital rinsing, light-based detection, biomarkers and mouth self examination (MSE), used singly or in combination, for the early detection of PMD or cancer of the lip and oral cavity in apparently healthy adults. SEARCH METHODS: We searched MEDLINE (OVID) (1946 to April 2013) and four other electronic databases (the Cochrane Diagnostic Test Accuracy Studies Register, the Cochrane Oral Health Group's Trials Register, EMBASE (OVID), and MEDION) from inception to April 2013. The electronic databases were searched on 30 April 2013. There were no restrictions on language in the searches of the electronic databases. We conducted citation searches, and screened reference lists of included studies for additional references. SELECTION CRITERIA: We selected studies that reported the diagnostic test accuracy of any of the aforementioned tests in detecting PMD or cancer of the lip or oral cavity. Diagnosis of PMD or cancer was made by specialist clinicians or pathologists, or alternatively through follow-up. DATA COLLECTION AND ANALYSIS: Two review authors independently screened titles and abstracts for relevance. Eligibility, data extraction and quality assessment were carried out by at least two authors independently and in duplicate. Studies were assessed for methodological quality using QUADAS-2. We reported the sensitivity and specificity of the included studies. MAIN RESULTS: Thirteen studies, recruiting 68,362 participants, were included. These studies evaluated the diagnostic accuracy of COE (10 studies), MSE (two studies). One randomised controlled of test accuracy trial directly evaluated COE and vital rinsing. There were no eligible diagnostic accuracy studies evaluating light-based detection or blood or salivary sample analysis (which tests for the presence of bio-markers of PMD and oral cancer). Given the clinical heterogeneity of the included studies in terms of the participants recruited, setting, prevalence of target condition, the application of the index test and reference standard and the flow and timing of the process, the data could not be pooled. For COE (10 studies, 25,568 participants), prevalence in the diagnostic test accuracy sample ranged from 1% to 51%. For the eight studies with prevalence of 10% or lower, the sensitivity estimates were highly variable, and ranged from 0.50 (95% confidence interval (CI) 0.07 to 0.93) to 0.99 (95% CI 0.97 to 1.00) with uniform specificity estimates around 0.98 (95% CI 0.97 to 1.00). Estimates of sensitivity and specificity were 0.95 (95% CI 0.92 to 0.97) and 0.81 (95% CI 0.79 to 0.83) for one study with prevalence of 22% and 0.97 (95% CI 0.96 to 0.98) and 0.75 (95% CI 0.73 to 0.77) for one study with prevalence of 51%. Three studies were judged to be at low risk of bias overall; two were judged to be at high risk of bias resulting from the flow and timing domain; and for five studies the overall risk of bias was judged as unclear resulting from insufficient information to form a judgement for at least one of the four quality assessment domains. Applicability was of low concern overall for two studies; high concern overall for three studies due to high risk population, and unclear overall applicability for five studies. Estimates of sensitivity for MSE (two studies, 34,819 participants) were 0.18 (95% CI 0.13 to 0.24) and 0.33 (95% CI 0.10 to 0.65); specificity for MSE was 1.00 (95% CI 1.00 to 1.00) and 0.54 (95% CI 0.37 to 0.69). One study (7975 participants) directly compared COE with COE plus vital rinsing in a randomised controlled trial. This study found a higher detection rate for oral cavity cancer in the conventional oral examination plus vital rinsing adjunct trial arm. AUTHORS' CONCLUSIONS: The prevalence of the target condition both between and within index tests varied considerably. For COE estimates of sensitivity over the range of prevalence levels varied widely. Observed estimates of specificity were more homogeneous. Index tests at a prevalence reported in the population (between 1% and 5%) were better at correctly classifying the absence of PMD or oral cavity cancer in disease-free individuals that classifying the presence in diseased individuals. Incorrectly classifying disease-free individuals as having the disease would have clinical and financial implications following inappropriate referral; incorrectly classifying individuals with the disease as disease-free will mean PMD or oral cavity cancer will only be diagnosed later when the disease will be more severe. General dental practitioners and dental care professionals should remain vigilant for signs of PMD and oral cancer whilst performing routine oral examinations in practice.

This article outlines how to perform a standard comprehensive extraoral and intraoral examination and the existing commercially available adjunctive techniques for the early detection of oral cancer and premalignant lesions. Visualization-based techniques (e.g., autofluorescence and chemiluminescence), toluidine blue vital staining, cytopathologic tests and high-risk human papillomavirus testing are discussed in detail, including the indications and protocols for use, their advantages and disadvantages and clinical cases.