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Diagnostic devices for detecting oral cancer.

In the U.S., it is estimated that 34,000 Americans will be diagnosed with oral and pharyngeal cancer this year, causing over 8,000 deaths. Worldwide, oral cancer is the sixth most common malignancy, with more than 400,000 new cases diagnosed each year. Oral cancer is more prevalent than cervical cancer and Hodgkin's lymphoma. One American dies every hour from oral and pharyngeal cancers. (1) Unfortunately, diagnosis of oral cancer is established twice as often at a later stage, resulting in poor prognosis. In these situations, the overall 5-year survival rate is less than 50%.

Oral squamous cell carcinoma accounts for over 90% of oral cancers. Lesions often present as leukoplakia, erythroplakia or erythroleukoplakia. Risk factors for oral cancer include tobacco, alcohol consumption, infections (including human papilloma virus), mucosal diseases, exposure to ultraviolet light, ionizing radiation, arsenic or industrial chemicals, chronic irritation and immunosuppression. Other cofactors include chronic periodontal disease, poor oral hygiene, ill-fitting dentures, sharp teeth and edentulism. (2) Surprisingly, an estimated 25% of oral cancer victims do not fit the traditional profile of older users of tobacco and alcohol as they have no risk factors.

Early detection of oral cancer can be accomplished through a variety of approaches. The conventional oral examination (COE) is the main approach used by dentists and dental hygienists to identify oral abnormalities. Once identified, a scalpel biopsy and histologic examination of the lesion can be performed to determine the definitive diagnosis. However, it is difficult to visually diagnose premalignant and malignant pathoses. As well, not all clinicians routinely perform a COE.

To improve opportunities for diagnosing oral lesions, adjunctive diagnostic techniques have been developed and marketed among the dental community. These devices include toluidine blue (TB) staining, light-based detection systems, narrow emission fluorescence and brush biopsy.

TB has been used for over 40 years to detect mucosal abnormalities. TB is a metachromatic vital dye that tends to bind preferentially to tissues undergoing rapid cell division to sites of DNA change associated with oral premalignant and malignant lesions. It has been useful for demarcating the extent of a lesion prior to surgical removal. An overall sensitivity of 93.5% and specificity of 73.3% had been previously reported. (3) However, a recent meta-analysis reported a wide range of variation with respect to sensitivity and specificity. (4) In addition, no randomized clinical trials have been conducted to assess TB.

Light-based detection systems use chemiluminescent light to enhance visualization techniques. A pre-rinse of 1% acetic acid solution is used, followed by examining the oral cavity with a blue-white light source. Three systems are currently on the market including ViziLite Plus with TBlue (Zila Pharmaceuticals), Microlux DL (AdDent) and Orascoptic DK (Orascoptic, a Kerr Corporation). The ViziLite system combines a blue-white light energy source with TB staining. The Microlux DL system uses a blue-white light-emitting diode and a diffused fiber-optic light guide. The Orascoptic DK system is a 3-in-1, battery-operated, hand-held LED instrument that has an oral lesion screening instrument attachment. These light-based detection systems can enhance visualization of oral white lesions, but they cannot distinguish between oral malignancy, premalignant lesions, benign keratosis and other mucosal inflammatory lesions. No published studies were found for the Microlux DL or Orascoptic DK systems. Several studies of the ViziLite Plus with TB demonstrated improvement in specificity, reduction of the false positive rate by 55.26% and increasing the negative predictive value to 100%. (4)

Narrow emission fluorescence involves exposure of the mucosa to the blue light spectra using the VELscope[R] device (LED Dental). Tissue undergoing neoplastic change, such as dysplasia and invasive carcinoma, will demonstrate a loss of fluorescence. This system has been promoted as useful in assessing lesion margins enhancing surgical management. A summary of 2 studies evaluating VELscope indicated both sensitivity and specificity were high. However, these studies were of known lesions confirmed by biopsy. This system was not studied in relation to use as an adjunct for detection of new lesions. (4)

Recently, a new multispectral fluorescence device has been introduced, the Identafi[TM] 3000 (Trimira[TM]). This system uses 3 distinct color wavelengths to distinguish lesion morphology purportedly reducing false positives. However, no published studies were found on this system.

Brush cytopathology using the OralCDx Brush Test system (Oral CDx Laboratories) involves the microscopic study of cell samples. A specialized brush that collects transepithelial cells are smeared onto a glass slide and sent to a laboratory for staining and analysis. A computer-based imaging system ranks the cells on the basis of degree of abnormal morphology followed by a cytopathologist who interprets the results. Reported accuracy, sensitivity and specificity results vary. Use of this test has been recommended for assessment of lesions the clinician might not investigate further.

Although the opportunity exists to utilize adjuncts in detecting precancerous and cancerous lesions, there appears to be a lack of definitive evidence to imply that any of these systems improve the sensitivity or specificity of oral cancer screening beyond COE alone. (5) Ultimately, the scalpel biopsy and histologic examination remain the gold standard for achieving definitive diagnosis. Nevertheless, early detection of oral squamous cell carcinoma will only occur if dental professionals are looking for it.

References

(1.) Oral Cancer Foundation. Oral Cancer Facts [Internet]. Cited May 8, 2009. Available from: http://www.oralcancerfoundation.org/facts. Accessed 5/8/09.

(2.) Bsoul SA, Huber MA, Terezhalmy GT. Squamous cell carcinoma of the oral tissues: A comprehensive review for oral healthcare providers. J Contemp Dent Pract. 2005;6(4):1-16.

(3.) Rosenberg D, Cretin S. Use of meta-analysis to evaluate tolonium chloride in oral cancer screening. Oral Surg Oral Med Oral Pathol. 1989;67(5):621-627.

(4.) Patton LL, Epstein JB, Kerr AR. Adjunctive techniques for oral cancer examination and lesion diagnosis: A systematic review of the literature. J Am Dent Assoc. 2008;139(7):896-905.

(5.) Lingen MW, Kalmar JR, Karrison T, Speight PM. Critical evaluation of diagnostic aids for the detection of oral cancer. Oral Oncol. 2008;44(1):10-22.

JoAnn R. Gurenlian, RDH, PhD

President, Gurenlian & Associates, Visiting Doctoral Faculty, Capella University
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Author:Gurenlian, JoAnn R.
Publication:Journal of Dental Hygiene
Date:Sep 22, 2009
Words:1007
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