Fluorescence bronchoscopy for detection of lung cancer

A system using the fluorescence bronchoscope has been designed for localization of small, early bronchogenic carcinoma by the fluorescence of previously injected hematoporphyrin derivative. The system included a 200W mercury vapor lamp and primary filter, flexible fiberoptic bronchoscope with special violet-transmitting light conductor, secondary filter, and image intensifier tube. Tests indicated the system could detect a tumor only 100 micron thick at the expected concentration of hematoporphyrin derivative: 1 microgram/gm at 48 to 96 hours following intravenous injection at a dosage of 2.5 mg/kg. Examination of resected specimens (six of lung, one of esophagus) showed positive fluorescence in all cases, with fluorescence visible beyond the region visible under conventional white light examination. Fluorescence bronchoscopy has been performed on four patients thus far. Positive fluorescence was observed in all three cases where the tumor had been known to occur. Positive fluorescence was also observed in the patient with sputum positive for lung cancer, but negative x-ray film findings. However, additional examinations are required to demonstrate the smallest lesion that can be detected in vivo.