Hexaminolevulinate-induced fluorescence endoscopy in patients with rectal adenoma and cancer:: a pilot study

Background. Fluorescence endoscopy is a promising new method for detection and treatment of premalignant and malignant lesions. The aim of this pilot study was to investigate the feasibility of hexaminolevulinate-based photodetection of rectal adenoma and cancer, including safety, dose finding, and efficacy. Methods: Ten patients with known rectal adenoma or cancer were sensitized by instillation of 3.2 mM of hexaminolevulinate as an enema. Fluorescence endoscopy was performed after retention of the enema for 30 to 60 minutes, followed by a rest time of up to 30 minutes before endoscopy. Biopsy specimens were taken from fluorescent and non-fluorescent areas and fluorescence microscopy studies were performed to assess the distribution of protoporphyrin IX fluorescence in different tissue layers. Adverse events were reported by direct questioning of all patients; skin photosensitivity, changes in biochemical tests of liver function, blood pressure and heart rate, and the occurrence of GI symptoms (nausea, vomiting) were recorded for 5 patients. Observations: Hexaminolevulinate-induced fluorescence endoscopy produced selective fluorescence of all rectal adenomas with intraepithelial neoplasia. For rectal cancer, there was only weak fluorescence or none at all. No hexaminolevulinate-induced side effect was observed. In two patients, fluorescence differentiated adenomas and hyperplastic polyps. Conclusions: Hexaminolevulinate-based fluorescence endoscopy (3.2 mM administered as an enema) in patients with rectal cancer and adenoma was well tolerated and produced no significant skin sensitivity or other side effects. The optimal duration of application is 30 to 45 minutes, with a rest time of 30 minutes. Selective fluorescence of adenoma with intraepithelial neoplasia suggests that hexaminolevulinate-based fluorescence endoscopy may be useful for detection of premalignant lesions.