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 intrac ellular accumulation of endogenous protoporphyrin IX in colon cancer. Proto porphyrin IX itself is a potential photosensitizer that, can be used for la ser light-induced fluorescence diagnosis. The aim of this study was to dete ct cancer in the rat colon before macroscopic visibility. Study Design/Materials and Methods: Multifocal colon carcinomas were induce d by weekly subcutaneous injections of 1,2-dimethylhydrazin-dihydrochloride in male Wistar rats. Local photosensitization was performed with an ALA co lon lavage. Red fluorescence (635 nm) was induced by green laser-light irra diation with an Ar-Dye Laser (514 nm) in the colon. Fluorescence was observ ed by the naked eye with a filter at < 515 nm to eliminate the excitation l ight. Results: Twenty-five Wistar rats developed 99 macroscopically visible carci nomas and four macroscopically visible dysplasias. The following laser-ligh t-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 fluorescenc e detection of invisible dysplasias and early colon cancer in the rat. Lase rs Surg. Med. 26:302-307, 2000. (C) 2000 Wiley-Liss, Inc.