Lam et al., Chest, Vol 103, 1993

Detection and Localization of Early Lung Cancer by Imaging Techniques

- Fluorescence bronchoscopy can be employed to

• localize the source of abnormal cells
• procuring premalignant tissue for molecular biology studies
• monitoring progress of patients in chemoprevention studies

- Precancerous early lung cancer lesions do not produce symptoms. By the time chest symptoms appear, the cancer is often advanced beyond curability.

- Lung cancer mortality may be reduced if it can be detected early at the in situ stage. This may prevent disease progression to the malignant stage.

- Yield of sputum cytology is low; improvements in the sensitivity of the method to detect cancer and better cytomorphology criteria are needed.

- Conventional white light bronchoscopy not accurate: Misses significant dysplasia or carcinoma in situ in about 10-20% of cases. Why?:

• carcinomas are only a few cell laters thick (0.2 to 1 mm) and a few millimeters in surface diameter
• since they are small and thin, they usually do not produce any visible abnoramlity on conventional white-light bronochoscopy

- Fluorescence bronchoscopy can be performed with or without fluorescing drugs.

With drugs:

• these drugs are preferentially retained in tumours
• bulk of research focused on hematoporphyrin derivative (HpD) or its partially purified form, dihematoporphyrin ether/ester (photofrin):
• HpD or photofrin emits red fluorescence when excited by violet light
• Since the concentration of HpD or photofrin is higher in malignant tumours than most nonmalignant tissue, tumours can thus be detected by their more intense fluorescence

Without drugs:

• Autofluorescence approach
• use of in vivo spectroscopy with a helium-cadmium laser (442 nm) for illumination showed a significant decrease in autofluorescence intensity, predominantly in the green region of the visible spectrum in areas with dysplasia or carcinoma in situ, compared to normal bronchial tissue.

- LIFE: Lung Imaging Fluorescence Endoscope

• comprises of a helium-cadmium laser, two image-intensified CDD cameras with green and red band-pass filters, a computer with imaging board and a color video monitor
• real time imaging
• even precancerous lesions (moderate and severe dysplasia) can be detected by this means
• sensitivity: 72.5%, specificity: 94% (white-light sensitivity: 48.4%, specificity same)

- Possible applications of the LIFE device:

• detecting and localizing early lung cancer
• staging the extent of endobronchial spread of bronchial cancers
• detecting and localizing premalignant lesions (moderate/severe dysplasia in chemoprevention studies
• providing a vehicle to educate bronchoscopists in recognizing subtle changes during routine bronchoscopy