A systematic review of test performance in screening for oral cancer and precancer

[Autofluorescence for the detection of potentially malignant and malignant lesions of the oral cavity lining]

INTRODUCTION

The sensitivity of visual examination for the diagnosis of oral cancers is estimated at 85% and its specificity at 97%. However, it is likely that numerous lesions remain undetected. The objective of this article was to review literature on the contribution of tissular autofluorescence to detect potentially malignant and malignant lesions of the oral cavity.

MATERIAL AND METHOD

The Medline database was consulted using the following keywords: fluorescence and cancer; autofluorescence and cancer; fluorescence and oral cancer; autofluorescence and oral cancer; Velscope(®) and oral cancer. Only original articles and clinical case reports on the oral cavity published in English since 1999 were considered.

RESULTS

Twenty-three publications were analyzed. Twelve studies concerned spectroscopy and 14 direct autofluorescence. The specificity of AF ranged between 75 and 100% in spectroscopy and between 39 and 100% in direct vision. The sensibility of the AF varied between 78 and 100% in spectroscopy and between 50 and 100% in direct vision.

DISCUSSION

The variability of results may be explained by selection bias. The main contribution of fluorescence is to highlight oral mucous membrane lesions and to help physicians to better locate them. The lack of AF specificity supports the contribution of histological examination which remains the reference examination for the diagnosis of potentially malignant lesions and cancers of the oral cavity.

Screening programmes for the early detection and prevention of oral cancer

BACKGROUND

Oral cancer is an important global healthcare problem, its incidence is increasing and late-stage presentation is common. Screening programmes have been introduced for a number of major cancers and have proved effective in their early detection. Given the high morbidity and mortality rates associated with oral cancer, there is a need to determine the effectiveness of a screening programme for this disease, either as a targeted, opportunistic or population based measure. Evidence exists from modelled data that a visual oral examination of high-risk individuals may be a cost-effective screening strategy and the development and use of adjunctive aids and biomarkers is becoming increasingly common.

OBJECTIVES

To assess the effectiveness of current screening methods in decreasing oral cancer mortality.

SEARCH STRATEGY

The following electronic databases were searched: the Cochrane Oral Health Group Trials Register (to 20 May 2010), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, Issue 2), MEDLINE via OVID (1950 to 20 May 2010), EMBASE via OVID (1980 to 20 May 2010) and CANCERLIT via PubMed (1950 to 20 May 2010). There were no restrictions regarding language or date of publication.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of screening for oral cancer or potentially malignant disorders using visual examination, toluidine blue, fluorescence imaging or brush biopsy.

DATA COLLECTION AND ANALYSIS

The original review identified 1389 citations and this update identified an additional 330 studies, highlighting 1719 studies for consideration. Only one study met the inclusion criteria and validity assessment, data extraction and statistics evaluation were undertaken by six independent review authors.

MAIN RESULTS

One 9-year RCT has been included (n = 13 clusters: 191,873 participants). There was no statistically significant difference in the age-standardised oral cancer mortality rates for the screened group (16.4/100,000 person-years) and the control group (20.7/100,000 person-years). A 43% reduction in mortality was reported between the intervention cohort (29.9/100,000 person-years) and the control arm (45.4/100,000) for high-risk individuals who used tobacco or alcohol or both, which was statistically significant. However, this study had a number of methodological weaknesses and the associated risk of bias was high.

AUTHORS' CONCLUSIONS

Although there is evidence that a visual examination as part of a population based screening programme reduced the mortality rate of oral cancer in high-risk individuals, whilst producing a stage shift and improvement in survival rates across the population as a whole, the evidence is limited to one study and is associated with a high risk of bias. This was compounded by the fact that the effect of cluster randomisation was not accounted for in the analysis. Furthermore, no robust evidence was identified to support the use of other adjunctive technologies like toluidine blue, brush biopsy or fluorescence imaging within a primary care environment. Further randomised controlled trials are recommended to assess the efficacy, effectiveness and cost-effectiveness of a visual examination as part of a population based screening programme.

Advances in fluorescence imaging techniques to detect oral cancer and its precursors

Oral cancer is a significant health problem in the USA and throughout the world. Most oral cancer patients are diagnosed at a late stage, when treatment is less successful and treatment-associated morbidity is more severe. A number of new diagnostic aids to conventional oral examination have recently been introduced to assist in the early detection of oral neoplasia. In particular, autofluorescence imaging has emerged as a promising adjunctive technique to improve early identification of oral premalignant lesions. Direct visual inspection of tissue autofluorescence has shown encouraging results in high-prevalence populations, but the technique requires subjective interpretation and depends on the visual recognition skills of the examiner. Capturing and analyzing digital fluorescence images can reduce subjectivity and potentially improve sensitivity of detection of precancerous changes. Recent studies of wide-field autofluorescence imaging in low-prevalence populations suggest that benign lesions such as inflammation may give rise to false-positive results. High-resolution fluorescence imaging is a new modality that can be used in conjunction with wide-field imaging to improve specificity by imaging subcellular detail of neoplastic tissues. The combination of wide-field and high-resolution fluorescence imaging systems with automated image analysis should be investigated to maximize overall diagnostic performance for early detection of oral neoplasia.

Oral cancer screening: what have we learnt and what is there still to achieve?

Oral cancer is an important global healthcare problem. In the UK, the incidence is increasing and late-stage presentation is common. Determining the feasibility of a national screening program for oral cancer is therefore an important step in the prevention of the disease. Evidence exists to suggest that an oral examination of high-risk individuals may be a cost-effective screening strategy. However, questions remain over which primary care environment would be the most suitable and the criteria for a positive screen and referral. Further research is needed in the form of clinical trials or demonstration studies in primary care. The impact on secondary care, the role of auxiliaries and training needs also need to be determined. In addition, the assessment of adjunctive aids and evaluation of potential biomarkers are considered important.

Primary Care Clinicians and the Detection and Referral of Potentially Malignant Disorders in the Mouth: A Summary of the Current Evidence

The importance of detecting oral malignant disease is paramount. Recent government strategies have placed an emphasis on the early detection of cancer. This paper presents a brief account of the current debate around the role of oral cancer screening and provides a summary of the results of three practice-based studies that were supported by the British Society for General Dental Surgery and the Faculty of General Dental Practice (UK).

Overall, there appears to be a lack of rigour among some general dental practitioners when screening for potentially malignant disorders and their incidence in dental practice is perceived to be low. Barriers remain to the implementation of smoking-cessation schemes and many general dental practitioners feel out of their depth in tackling the abuse of alcohol, despite recognising its importance as a risk factor. Patients continue to present to their general medical practitioner (GMP) when they are concerned about something in their mouth that is not related to their teeth. GMPs’ ability to manage early oral cancer is discussed.

A prospective randomised controlled trial (RCT), or a demonstration study, is recommended to investigate the numbers of cases of oral cancer diagnosed in primary dental care and primary medical care and to develop standardised referral criteria for early cases of this disease to reduce under- and over-referral. The RCT could also examine the potential of using auxiliary healthcare workers and examine the impact of such a programme upon secondary care services.

The assessment of diffused light illumination and acetic acid rinse (Microlux/DL) in the visualisation of oral mucosal lesions

Oral examination alone cannot always distinguish benign from premalignant and malignant lesions, thereby resulting in delayed patient referral and poorer prognosis. Thus, any non-invasive technology which highlights oral premalignant and malignant lesions in a highly sensitive and specific manner will undoubtedly aid clinicians in early diagnosis and treatment of these conditions. The aim of this study was to assess the efficacy of acetic acid mouthwash and diffused light illumination (Microlux/DL) as a diagnostic aid in the visualisation of oral mucosal lesions and its ability to highlight malignant and potentially malignant lesions. Fifty patients referred for assessment of an oral white lesion were initially examined under routine incandescent operatory light. The location, size, ease of visibility, border distinctness and presence of satellite lesions were recorded. Clinical examination was repeated using the Microlux/DL diffused light illumination kit. An incisional biopsy was performed to provide a definitive histopathological diagnosis. Microlux/DL examination enhanced the visibility of 34 lesions, however, it did not help uncover any clinically undetected lesions, change the provisional diagnosis, or alter the biopsy site. Microlux/DL showed a sensitivity of 77.8% and a specificity of 70.7%, with a positive predictive value of 36.8%. Although Microlux/DL appears useful at enhancing lesion visibility, it is a poor discriminator for inflammatory, traumatic and malignant lesions.

Objective detection and delineation of oral neoplasia using autofluorescence imaging

Although the oral cavity is easily accessible to inspection, patients with oral cancer most often present at a late stage, leading to high morbidity and mortality. Autofluorescence imaging has emerged as a promising technology to aid clinicians in screening for oral neoplasia and as an aid to resection, but current approaches rely on subjective interpretation. We present a new method to objectively delineate neoplastic oral mucosa using autofluorescence imaging. Autofluorescence images were obtained from 56 patients with oral lesions and 11 normal volunteers. From these images, 276 measurements from 159 unique regions of interest (ROI) sites corresponding to normal and confirmed neoplastic areas were identified. Data from ROIs in the first 46 subjects were used to develop a simple classification algorithm based on the ratio of red-to-green fluorescence; performance of this algorithm was then validated using data from the ROIs in the last 21 subjects. This algorithm was applied to patient images to create visual disease probability maps across the field of view. Histologic sections of resected tissue were used to validate the disease probability maps. The best discrimination between neoplastic and nonneoplastic areas was obtained at 405 nm excitation; normal tissue could be discriminated from dysplasia and invasive cancer with a 95.9% sensitivity and 96.2% specificity in the training set, and with a 100% sensitivity and 91.4% specificity in the validation set. Disease probability maps qualitatively agreed with both clinical impression and histology. Autofluorescence imaging coupled with objective image analysis provided a sensitive and noninvasive tool for the detection of oral neoplasia.

Critical evaluation of diagnostic aids for the detection of oral cancer

Historically, the screening of patients for signs of oral cancer and precancerous lesions has relied upon the conventional oral examination. A variety of commercial diagnostic aids and adjunctive techniques are available to potentially assist in the screening of healthy patients for evidence of otherwise occult cancerous change or to assess the biologic potential of clinically abnormal mucosal lesions. This manuscript systematically and critically examines the literature associated with current oral cancer screening and case-finding aids or adjuncts such as toluidine blue, brush cytology, tissue reflectance and autofluorescence. The characteristics of an ideal screening test are outlined and the authors pose several questions for clinicians and scientists to consider in the evaluation of current and future studies of oral cancer detection and diagnosis. Although the increased public awareness of oral cancer made possible by the marketing of recently-introduced screening adjuncts is commendable, the tantalizing implication that such technologies may improve detection of oral cancers and precancers beyond conventional oral examination alone has yet to be rigorously confirmed.

Prevalence of oral cancer and pre-cancer and associated risk factors among tea estate workers in the central Sri Lanka

BACKGROUND

To screen for oral cancer or not is being debated, but for high-risk populations with minimal access to regular dental care systematic oral examinations could provide some benefit.

METHODS

We undertook oral mucosal examinations of labourers employed in tea estate plantations in Sri Lanka. In a two-stage screening procedure, first by estate medical officers and then by visiting specialists, we examined 12 716 persons at their workplaces achieving a coverage of one-sixth of the total workforce.

RESULTS

Fourteen oral cancers and 848 subjects with oral pre-cancer (6.7%) were detected giving population prevalences of 46.1 per 1000 for leukoplakia and 16.4 per 1000 for oral submucous fibrosis. Among subjects with any oral mucosal disorder (n = 1159) proportions of current users of betel quid, smokers and alcohol use was recorded at 92%, 31% and 61% respectively. The synergistic effect of these three risk habits on the development of oral leukoplakia was evident in mixed habit groups.

CONCLUSIONS

The prevalence of oral pre-cancer in tea estate labourers was higher than estimates reported in previous studies. In the absence of state-sponsored preventive activities, it is necessary to improve the capacity of individual health practitioners and small medical centres to participate in oral health promotion and oral cancer/pre-cancer screening.

Oral cancer: experiences and diagnostic abilities elicited by dentists in North-western Spain

BACKGROUND

Opinions, knowledge, behaviours and attitudes of general dental practitioners on oral cancer prevention and detection have been reported from many countries. However, experiences and skills of oral cancer detection have not been evaluated systematically.

OBJECTIVE

To obtain information on behaviours of screening and ability to correctly detect oral cancer and precancer among general dentists (GDP) in North-western Spain.

SUBJECTS AND METHODS

Thirty-two randomly selected GDPs completed questionnaires and then classified 50 projected images of clinical lesions, into cancer, precancer or benign lesions.

RESULTS

87.5% reported conducting routine oral examinations, 84.4% provided routine advice to their subjects for risk modifications and 84.4% claimed to biopsy a suspected oral mucosal lesion that they detected in practice. In a quasi research setting using clinical slides, the sensitivity of visual diagnosis of a cancerous lesion was 61.4% and precancer 59.5%. The diagnostic accuracy reported here is lower than what is already reported by evaluation of published screening programmes by dentists.

CONCLUSIONS

Our data from Spain suggest a need for improving the diagnostic ability of GDPs in the visual detection of oral cancer/precancer by strengthening continuing professional education.

Screening programmes for the early detection and prevention of oral cancer

BACKGROUND

Screening programmes for major cancers, such as breast and cervical cancer have effectively decreased the mortality rate and helped to reduce the incidence of these cancers. Although oral cancer is a global health problem with increasing incidence and mortality rates, no national population-based screening programmes for oral cancer have been implemented. To date there is debate on whether to employ screening methods for oral cancer in the daily routine work of health providers.

OBJECTIVES

To assess the effectiveness of current screening methods in decreasing oral cancer mortality.

SEARCH STRATEGY

Electronic databases (MEDLINE, CANCERLIT, EMBASE, the Cochrane Central Register of Controlled Trials; 1966 to July 2005, The Cochrane Library - Issue 3, 2005), bibliographies, handsearching of specific journals and contact authors were used to identify published and unpublished data.

SELECTION CRITERIA

Randomised controlled trials of screening for oral cancer or precursor oral lesions using visual examination, toluidine blue, fluorescence imaging or brush biopsy.

DATA COLLECTION AND ANALYSIS

The search found 112 citations and these have been reviewed. One randomised controlled trial of screening strategies for oral cancer was identified as meeting the review's inclusion criteria. Validity assessment, data extraction and statistics evaluation were undertaken by two independent review authors.

MAIN RESULTS

One 10-year randomised controlled trial has been included (n = 13 clusters: 191,873 participants). There was no difference in the age-standardised oral cancer mortality rates for the screened group (16.4/100,000 person-years) and the control group (20.7/100,000 person-years). Interestingly, a significant 34% reduction in mortality was recorded in high-risk subjects between the intervention cohort (29.9/100,000 person-years) and the control arm (45.4/100,000). However, this study has some methodological weaknesses. Additionally, the study did not provide any information related to costs, quality of life or even harms of screening from false-positive or false-negative findings.

AUTHORS' CONCLUSIONS

Given the limitation of evidence (only one included randomised controlled trial) and the potential methodological weakness of the included study, it is valid to say that there is insufficient evidence to support or refute the use of a visual examination as a method of screening for oral cancer using a visual examination in the general population. Furthermore, no robust evidence exists to suggest that other methods of screening, toluidine blue, fluorescence imaging or brush biopsy, are either beneficial or harmful. Future high quality studies to assess the efficacy, effectiveness and costs of screening are required for the best use of public health resources. In addition, studies to elucidate the natural history of oral cancer, prevention methods and the effectiveness of opportunistic screening in high risk groups are needed. Future studies on improved treatment modalities for oral cancer and precancer are also required.

A systematic review of measures of effectiveness in screening for oral cancer and precancer

Nine databases were searched for studies reporting a range of measures on the effectiveness of screening for oral cancer and precancer in primary care. Of 1114 papers generated in a search of nine databases, full texts of 90 were scrutinised by two reviewers to ensure that they were concerned with oral cancer/precancer, reported an oral cancer screening programme/exercise and included at least one effectiveness outcome. Criteria for considering studies for the review covered types of studies, participants, interventions and outcome measures. The latter included measures of both end point and interim outcome and also process. Of 90 full text articles screened, examiners agreed on the inclusion of 28 (initial agreement -- kappa=0.60). The remaining 62 were excluded and the reasons recorded. The studies included showed substantial heterogeneity regarding objectives and study design, location and setting, numbers and characteristics of participants, screening personnel, methods of recruitment and types of data collected. Only one study, from the Indian sub-continent, reported a randomised controlled trial: interim results showed 14.9% of intervention subjects died after 3 years compared with 56.3% of non-intervention controls. The review overall produced no evidence in favour of or against the potential benefits associated with an oral cancer screening programme. It was concluded that there are insufficient available data to make an unequivocal determination as to the effectiveness of oral cancer screening programmes at the present time. However, a recent further report on the Indian study published after completion of the review, provides some evidence that screening for oral cancer may be effective, at least in developing countries with a high incidence of the disease.