Photodynamic diagnosis of gastrointestinal precancerous lesions after sensitization with 5-aminolaevulinic acid: a pilot study

Basic problem and objective: Endoscopic diagnosis of gastrointestinal precancerous and cancerous lesions is difficult, often even impossible. This study was undertaken to find out whether premalignant or suspected malignant tumors can be diagnosed by preceding sensitization with 5-amino-laevulinic acid (ALA), which in tumors is transformed in increased amounts into photosensitizing protoporphyrin IX, the latter being recognized by its characteristic red fluorescence on exposure to blue light. Patients and methods: 20 patients with known mild or moderately severe dysplasias (Barrett's esophagus, n=8; colorectal adenoma, n=3; ulcerative colitis n=2, and gastric polyps or mucosal changes suspicious of malignancy, n=5. Two patients with squamous-cell carcinoma, who after radio-and chemotherapy were endoscopically free of tumor, were sensitized with different concentrations of ALA (orally: 5 -30 mg/kg; or locally: 3 g in 100 ml 0.9% NaCl). Photodynamic diagnosis (PDD) took place 4-8 h after oral and ca. 1 -2 h after local sensitization with blue light (D-light, Storz, Tuttlingen, Germany). Results: Definite red fluorescence with demonstration of dysplasia was found in three of four patients with Barrett's esophagus. Biospies from nonfluorescent areas were free of dysplasia. Two gastric adenomas (10 mg/kg ALA with high-grade dysplasia were definitively endoscopically by their red fluorescence. In one patient mild dysplasia was found in a nonfluorescent area after radio-and chemotherapy of an esophageal carcinoma. Dysplasias were also seen in the rectal biopsy after local applications. Conclusion: PDD makes it possible for the first time to visualize precancerous lesions of the gastrointestinal tract after preceding ALA sensitization. PDD is a highly promising method for monitoring patients with gastrointestinal disease and an increased risk of cancer, and for clarifying the diagnosis of mucosal changes suspicious of malignancy.