OPTICAL DIAGNOSTICS: Blue light screens for oral cancer

A handheld optical tool designed to screen for high-risk oral lesions in real time shows promise for early, noninvasive detection of oral cancer, according to researchers supported by the National Institute of Dental and Craniofacial Research (NIDCR; Bethesda, MD), part of the National Institutes of Health. The visually enhanced lesion scope (VELScope) uses fluorescence to enable dentists to visualize whether a patient might have a developing oral cancer.

Oral premalignant lesions can indicate oral squamous-cell carcinoma, which causes more than 100,000 deaths worldwide each year. Early detection of this oral cancer enables minimally invasive treatment procedures and greatly enhances the chance of survival.

The instrument emits a cone of blue light into the mouth to excite various molecules within cells. Blue light (400 to 460 nm) excites green-red fluorescence in the oral tissues and enables the direct visualization of fluorescence in the context of surrounding normal tissue (see figure). The cone of blue excitation light emitted from the VELscope unit produces a spot 44 mm in diameter on the tissue at a distance of 100 mm. The device comprises a benchtop light source using a 120 W metal halide arc lamp with an integral elliptical reflector optimized for near-UV/blue reflection.

Changes in the natural fluorescence of healthy tissue generally reflect light-scattering biochemical or structural changes that indicate developing tumor cells. Thus, dentists can use the VELScope to shine a light onto a suspicious sore in the mouth, look through an attached eyepiece, and watch directly for changes in color. According to the researchers, normal oral tissue emits a pale green fluorescence, while potentially early tumor, or dysplastic, cells appear dark green to black.

Miriam Rosin, a cancer biologist at the British Columbia Cancer Research Center in Vancouver, Canada, explained that the natural fluorescence of the mouth is invisible to the naked eye. The VELScope provides a way to visualize the biological information and enable it to tell pathologists whether a lesion is likely to become cancerous. Then they can choose the appropriate course of therapy.

In a study, the VELScope demonstrated 98% sensitivity and 100% specificity in discriminating normal oral mucosa from cancerous or precancerous tissue.1 Scientists evaluated 50 tissue sites taken from 44 people. The pathologists performed biopsies on all of the sites and classified seven as normal, 11 as having severe dysplasia, and 33 as having oral squamous-cell carcinoma. Using VELscope to read the fluorescence patterns of the 50 sites, the group correctly identified all of the normal biopsies, 10 of the severe dysplasias, and all of the cancers.

Rosin’s group is now engaged in a larger follow-up study in Vancouver to further evaluate the VELScope for oral cancer, while other groups are evaluating it for detection of lung and cervical cancer. LED Medical Diagnostics (Vancouver, BC, Canada) is attempting to obtain FDA clearance and commercialize the VELScope.

REFERENCE

1. Pierre M. Lane et al., J. Biomed. Opt. 11