5-Aminolevulinic acid-induced fluorescence endoscopy for the detection of lower urinary tract tumors

The use of a photodynamic fluorescence marker for diagnosis of tumors is an intriguing concept to improve the thoroughness of surgical tumor resection. Complete surgical resection of multifocal bladder tumors and flat lesions such as carcinoma in situ is known to be difficult, and thus a source of recurrences. We report on the recent experience with the intravesical application of the photosensitizer prodrug 5-aminolevulinic acid (5-ALA), which is a nontoxic physiological heme substrate. Initial results from fluorescence diagnosis using krypton laser light, and recent results with a modified incoherent light source constantly showed a 25% increase in urothelial tumor detection in comparison to white light endoscopy. Due to the high sensitivity, the number of biopsies could be decreased constantly in comparison to routine random biopsies taken under white light endoscopy. The results show about 25-30% of cases with fluorescent lesions which are histologically benign. 5-ALA is a promising tool for the diagnosis of bladder cancer. The outcome of the admission study for 5-ALA in urology in Germany is positive, and is being continued by prospective multicenter clinical studies to prove the hypothesis of reduction of tumor recurrence with this method. 5-ALA-based fluorescence endoscopy is strongly recommended for further clinical testing.