Lam et al., Chest, Vol. 113, 1998

Localization of Bronchial Intraepithelial Neoplastic Lesions by Fluorescence Bronchoscopy

- Lung cancer patients have low survival rates because tumours are found at a late invasive stage, when the options for treatment are mostly palliative.

(Palliative treatment = treatment that concentrates on reducing the severity of disease symptoms or slowing the disease's progress, rather than providing a cure)

- Experience in other epithelial organs such as the cervix, esophagus and colon has shown that if the neoplastic lesions can be detected and treated in the intraepithelial stage, the cure rate can be significantly improved (2-4).

2. Anderson GH, Boyes DA, Benedet JL, et al. Organization and results of the cervical cytology screening program in British Columbia, 1955-85. BMJ 1988; 296:975-78
3. Winawer SJ, Zauber AG, Ho MN, et al. Prevention of colorectal cancer by colonoscopic polypectomy. N Engl J Med 1993; 329:1977-81
4. Jiang T, Yan S, Zhao L. Preventing effect of ‘liuwei dihuang decoction’ on esophageal carcinoma. Jpn J Cancer Chemother 1989; 16:1511-18

- Unfortunately in the tracheobronchial tree, identifying these leasions and localizing their exact sites remain problematic.

- During illumination of the bronchial (or any other tissue) surface, light can be:

• reflected
• back-scattered
• absorbed
• induce tissue fluorescence

- Conventional white light bronchoscopy makes use of the first 3 optical properties - reflectance imaging.

- Tissue autofluorescence is not visible to the unaided eye because its intensity is very low and overwhelmed by the reflected and back-scattered light. It can only be visualized with suitable instrumentation.

- Fluorescence intensities differ significantly between normal and neoplastic tissues - this difference can be exploited to enhance our ability to localize areas of intraepithelial neoplasia in the tracheobronchial tree.

- Using Monte-Carlo simulation, one of the major causes for the loss of autofluorescence in areas of dysplasia or cancer was found to be a decrease in the extracellular matrix content (31, 32)

31 Qu J, MacAulay C, Lam S, et al. Optical properties of normal and carcinoma bronchial tissue. Appl Optics 1991; 11: 99-105
32 Qu J, MacAulay C, Lam S, et al. Laser induced fluorescence spectroscopy at endoscopy: tissue optics; Monte Carlo modeling and in vivo measurements. Optical Eng 1995; 34: 3334-43

- Only a proportion of the dysplastic lesions expressed matrix metalloproteinases that can degrade the extracellular matrix (30)

30 Bolon I, Brambilla E, Vandenbunder B, et al. Changes in the expression of matrix proteases and of the transcription factor c-Ets1 during progression of precancerous bronchial lesions. Lab Invest 1996; 75: 1-13

- Fluorescence bronchoscopy has made it possible to allow sampling of intraepithelial neoplastic lesions in vivo, especially serial sampling of the same area over time to study the pathogenesis of lung cancer and the natural history of these lesions.