DUBLINA new diagnostic strategy using fluorescence bronchoscopy has proven six times more sensitive than white-light bronchoscopy alone in picking up preinvasive lung lesions, Stephen Lam, MD, of the University of British Columbia, reported at the 8th World Conference on Lung Cancer.
We cant afford to say no to early detection and treatment of lung cancer, Dr. Lam argued, pointing out that, for preinvasive and microinvasive tumors less than 1 cm in size, the overall cure rate following endobronchial photodynamic therapy is close to 90%. So the key is to detect these lesions when theyre very small, he said. We can have very good treatment, but unless we can find these cases, the impact on overall lung cancer mortality will be minimal.
The lung imaging fluorescence endoscope (LIFE) system, a laser device that can be attached to a fiberoptic bronchoscope (see Figure 1 ), makes use of the optical properties of the bronchial tissue. Upon exposure to a blue laser light, normal bronchial tissue fluoresces green whereas neoplastic tissues lose fluorescence intensity and appear brown or brownish red, depending on the pathology grade (see Figure 2 )
The power of the technique is such that it can show very small clusters of malignant cellsabout 1 mm in sizethat would be invisible with conventional bronchoscopy. Whats more, quan-titation of the fluorescence intensity reveals that the ratio of the red area to the green area is significantly greater, not only in patients with frank pathologic abnormalities but also in those with certain genetic changes.
700 Biopsies Evaluated
Dr. Lam described a seven-center North American study that evaluated 700 fluorescence-bronchoscopy-directed biopsies as well as random lung biopsies, turning up 93 cases of moderate or severe dysplasia, nine of carcinoma in situ, and 40 of invasive carcinoma.
When we looked at the relative sensitivity of conventional white-light bronchoscopy alone vs combined white-light and fluorescence bronchoscopy, we found that conventional bronchoscopy detected only 35 of the total of 142 lesions, he said. But using the combined examination, we were able to pick up 95 of these lesions.
Since the ultimate goal is to catch preinvasive lesions, however, Dr. Lam and his co-investigators went a step further and compared the ability of the two approaches in detecting dysplasia and carcinoma in situ.
Using white-light bronchoscopy alone, we could pick up only 9% of these preinvasive lesions, but with the combined examination, we picked up 56%, for a relative sensitivity of 6.3, Dr. Lam pointed out.
The false-positive rate was 10% with white-light bronchoscopy and 34% with the combination technique, he said.
The Vancouver group is also applying fluorescence bronchoscopy as a tool to screen for bronchial dysplasia and carcinoma in situ in healthy current and former smokers.