INHALATION OF 5-AMINOLEVULINIC ACID - A NEW TECHNIQUE FOR FLUORESCENCE DETECTION OF EARLY-STAGE LUNG-CANCER

Topical application of 5-aminolevulinic acid (5-ALA), with subsequent synthesis of protoporphyrin IX (PPIX),is a novel outstanding procedure for photodynamic treatment. So far, clinical experience has been repo rted with creams containing 5-ALA for the therapy of skin cancer, oral application for the treatment of gastrointestinal disease and intrave sical instillation of 5-ALA solutions for fluorescence detection of su perficial bladder cancer. Inhalation of 5-ALA for the staining of bron chial malignancies is a preferred method in clinical pulmonology. Sinc e no adverse reaction was observed in lung function in a canine follow ing inhalation of 5-ALA in increasing concentrations, clinical applica tions were performed. Seven patients with positive or suspicious sputu m cytology, but negative white light bronchoscopy, received 5-10 wt.% 5-ALA in NaCl solution by means of a medical nebulizer. No side effect s were observed during and after 5-ALA inhalation. After a period of 3 h, patients underwent fluorescence bronchoscopy using violet light fo r fluorescence excitation and an optical multichannel analyzer for flu orescence detection in situ. The results showed fluorescence spectra w hich could be related to PPIX induced by 5-ALA in the bronchial mucosa . The fluorescence intensity was sufficiently high for video imaging u sing a target integrating color CCD camera adapted to the flexible bro nchoscope. Carcinoma in situ, as well as dysplasias, showed a clear po sitive fluorescence. A correlation of fluorescence contrast with histo logy on 30 biopsies revealed a high sensitivity, but a specificity bel ow 50%. Improvements in light and drug dosimetry will form the basis f or further clinical trials.