December 20, 2006
One of the cornerstones of modern medicine is that patients receive a rapid and accurate diagnosis. But for dentists who suspect a patient might have an early oral tumor, a rapid-and-accurate diagnosis is a technologically formidable task, in part, because of an inability to properly visualize the abnormality and gain access to its molecular information that would indicate a tumor. A team of NIDCR grantees and colleagues has begun to develop new and existing visualization tools to solve this problem. One tool now under development is called the VELscope. It is a simple hand-held device that emits a cone of blue light into the mouth that excites various molecules within the tissue, causing it to absorb the light energy and re-emit it as visible fluorescence. Because changes in the natural fluorescence of healthy tissue generally are different from those indicative of developing tumor cells, the VELscope allows dentists to watch directly for telltale differences in color.
Following up on their initial work published in early 2006, the scientists report in the November 15 issue of the journal Clinical Cancer Research that the VELscope fared extremely well clinically in characterizing oral tissue biopsies rapidly and accurately. In a study of 20 consecutive patients who arrived at an operating room with histologically confirmed oral cancer, the group found that all tumors had changes in fluorescence that the VELscope detected. Their data were generated from a total of 122 oral mucosa biopsies - 20 from the tumors themselves and 102 from the tumor margins. Importantly, 19 of the 20 tumors had fluorescence changes that extended in at least one direction beyond the clinically visible tumor. These extensions, which are undetectable with the unaided eye and thus might go untreated, extended from 4 to 25 millimeters from the visible lesion.
“One of the most difficult and contentious issues with respect to treatment of oral cancers involves the decision on the width of clinically normal tissue that should be removed in addition to the tumor,” the authors noted. “In an effort to remove occult high-risk field change, surgeons frequently remove an arbitrary 10 mm or more of normal-looking mucosal margin when excising oral cancer, if anatomically possible. Unfortunately, this approach still fails to completely remove the occult high-risk field changes of many patients, resulting in a high rate of tumor recurrence . . . If a 10-mm clearance of clinical tumor was used arbitrarily in this sample set, half of the 20 tumors in this study would have cancer or dysplasia at the surgical margin, with six cases (30%) showing severe dysplasia or CIS. These six tumors would have a high chance of tumor recurrence because of the inadequate removal.”