Evaluating the efficacy and safety of a novel endoscopic fluorescence imaging modality using oral 5-aminolevulinic acid for colorectal tumors

Background and study aims: Five-aminolevulinic acid (5-ALA) is being increasingly used for photodynamic diagnosis and therapy of various types of tumors including brain, urologic, and other neoplasias. The use of 5-ALA to treat Barrett’s carcinomas has been documented, but its clinical effectiveness for diagnosis of gastrointestinal tumors, particularly early cancers, remains unknown. Patients and methods: The aim of our feasibility study was to evaluate the visibility of colorectal tumors using endoscopic fluorescence imaging (EFI) after oral administration of 5-ALA. The lesions identified by direct visualization and by the spectrums produced using EFI modality with 5-ALA were compared to the clinicopathologic features of resected specimens. Results: Twenty-three patients with a total of 27 known colorectal lesions were enrolled in the study. The median tumor size was 30 mm (range 10 – 75). Eleven of the lesions were flat or depressed lesions and 16 were sessile. Red fluorescence was observed in 22 out of 27 lesions. Red fluorescence was negative in 4 out of 11 flat or depressed lesions. In comparison with histopathologic findings, the rates of red fluorescence visibility were 62.5 % in low-grade intraepithelial neoplasia, 77.8 % in high-grade neoplasia, and 100 % in submucosal carcinoma. Red fluorescence visibility increased with the degree of dysplasia. There were no significant adverse events identified in this study. Conclusions: This feasibility study using EFI with 5-ALA demonstrated high visibility of superficial colorectal neoplasia. EFI with 5-ALA appears to be a novel, safe technique for improving real-time colorectal tumor imaging.