Local 5-aminolevulinic acid application for laser light-induced fluorescence diagnosis of early staged colon cancer in rats.

BACKGROUND AND OBJECTIVES

5-Aminolevulinic acid (ALA) increases the intracellular accumulation of endogenous protoporphyrin IX in colon cancer. Protoporphyrin IX itself is a potential photosensitizer that can be used for laser light-induced fluorescence diagnosis. The aim of this study was to detect cancer in the rat colon before macroscopic visibility.

STUDY DESIGN/MATERIALS AND METHODS: Multifocal colon carcinomas were induced by weekly subcutaneous injections of 1,2-dimethylhydrazin-dihydrochloride in male Wistar rats. Local photosensitization was performed with an ALA colon lavage. Red fluorescence (635 nm) was induced by green laser-light irradiation with an Ar-Dye Laser (514 nm) in the colon. Fluorescence was observed by the naked eye with a filter at < 515 nm to eliminate the excitation light.

RESULTS

Twenty-five Wistar rats developed 99 macroscopically visible carcinomas and four macroscopically visible dysplasias. The following laser-light-induced fluorescence diagnosis procedure was able to detect 16 additional carcinomas and 41 additional dysplasias.

CONCLUSIONS

Local ALA application induces a tumor-specific protoporphyrin IX accumulation in the rat colon and is an efficient method for fluorescence detection of invisible dysplasias and early colon cancer in the rat.