Camile S. Farah, BDSc, MDSc, PhD, discusses the role of optical adjunctive devices for the early detection of oral cancer and potentially malignant lesions.
Q: What are optical adjunctive devices (OADs), and what are they used for?
A: OADs are handheld tools designed to improve detection and visualization of oral mucosal pathology. They emit light at a particular wavelength that does one of the following (1) illuminates oral mucosal tissues and is reflected (reflectance devices incorporating white light); (2) excites endogenous fluorophores such as amino acids, metabolic products, and structural proteins to emit lower-energy photons (fluorescence devices emitting violet or blue excitation light); or (3) enhances the underlying vasculature of the mucosa to provide additional information regarding the vascular or inflammatory nature of the tissue (reflectance spectroscopy). OADs are effective in assisting with the detection and visualization of oral mucosal abnormalities; however, more research is needed to evaluate their ability to differentiate benign lesions from potentially malignant and malignant lesions.
Q: Are there any technical or biological issues that should be considered when using OADs for screening oral lesions?
A: Like any diagnostic tool, OADs should be used per manufacturer instructions, and only after suitable training; otherwise, the likelihood of false positive or negative results is increased. Reflectance devices that emit white light typically do not cause problems for clinicians, as they are more familiar with direct light visualisation of oral mucosal structures. Fluorescence and spectroscopy devices require a technical understanding of light, its composition, scattering and absorption profile, and the biology of mucosal tissues. Use of any of the devices requires an enhanced understanding of oral mucosal anatomy and pathology. In the case of fluorescence devices, it should be remembered that vascular, hemorrhagic, and pigmented lesions in addition to areas of exogenous staining (such as amalgam tattoos) will all lose autofluorescence. Applying pressure to the lesion, known as diascopy, can help determine if the lesion is vascular/inflammatory, as both these lesion types will blanch under pressure; whereas hemorrhagic lesions (such as petechia/purpura), pigmented lesions, and foreign bodies (such as amalgam) will not.
Q: What types of devices are available for detecting oral cancer and precancerous lesions?
A: OADs come in different shapes, sizes, and price ranges. There are 3 categories—reflectance, fluorescence, spectroscopy—or combinations thereof that allow the clinician to either visualize epithelial surface changes or probe deeper mucosal tissues.
Some white light reflectance devices include Orascoptic’s Discovery headlight, AdDent’s battery-operated intraoral LED Microlux DL transilluminator with diffused light attachment, or the white light feature of DentalEZ’s Identafi or Olympus’ Narrow Band Imaging (NBI) system. Fluorescence devices include LED Dental’s VELscope, Identafi, Forward Science’s OralID, AdDent’s Bio/Screen, and DentMat’s ViziLite PRO, all of which operate by emitting blue or violet excitation light at 405 to 450 nm and require visualization through a filter incorporated into the device or worn by the operator. Spectroscopy devices include Identafi or the NBI system. NBI’s blue light centered at 415 nm corresponds to the main peak absorption spectrum of hemoglobin and penetrates the superficial mucosal layer, whereas blood vessels in the deeper mucosal and submucosal layers are visualized due to the deeper penetration of green light centered at 540 nm. In the case of Identafi, its green-amber light emits at 545 nm.
Several devices incorporate more than one light technology/wavelength, such as a combination of reflectance, fluorescence, and spectroscopy in the case of Identafi (handheld multispectral device); or reflectance and spectroscopy in the case of NBI (endoscopic device). In such cases, the clinician should follow the manufacturer’s operating instructions and use the correct light sequence of reflectance, then fluorescence or spectroscopy to avoid false positive findings and to sequentially add clinical value to the oral examination by assessing color, texture, and ulceration under white light, loss of autoflorescence and diascopy under blue/violet light, and then the vascular/inflammatory nature of the lesion under green-amber light.
Q: Are there groups of patients who would more likely benefit from the use of OADs?
A: Incorporating the use of one or more of the OADs into a routine clinical oral examination is a good way of maximizing their utility and increasing the likelihood of detecting mucosal pathology. In fact, a specific decision-making protocol should be adopted to avoid false-positive findings and to enhance the utility of these devices in the general dental practice.
Given that a general dental practitioner is more likely to encounter oral potentially malignant lesions (OPMLs) (such as leukoplakia) in daily practice compared to oral cancer, it is advisable to assess all high-risk patients with OADs as part of a comprehensive head and neck cancer examination and risk assessment. Patients at high risk for oral cancer include older males (> 60 years) with a history of smoking and alcohol consumption; patients with a family history of upper aero-digestive cancer; and those with OPML (such as leukoplakia, erythroplakia, oral lichen planus, discoid lupus erythematosus, chronic hyperplastic candidosis) particularly involving the lateral border of tongue or floor of mouth. Patients at high risk for malignant transformation of oral leukoplakia (the most common OPML) include nonsmoking older females (> 60 years) who present with a nonhomogenous, multifocal lesion larger than 200 mm2 present on the lateral border of tongue or floor of mouth, which has been present for less than 5 years or demonstrates oral epithelial dysplasia on biopsy.
Dr. Farah is a professor of oral oncology, dean and head of the University of Western Australia (WA) School of Dentistry, and director of the Oral Health Centre of WA at the university. A Fellow of the Royal Australasian College of Dental Surgeons (Australia) in oral medicine, he has written 132 peer-reviewed publications and 16 book chapters and has attracted competitive research funding. His research interests in oral oncology span optical imaging systems, molecular genomics, and clinical trials in early cancer detection and surgical margin delineation. He can be reached via email at camile.farah@uwa.edu.au.
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