FLUORESCENCE PHOTODETECTION OF NEOPLASTIC LESIONS IN THE ORAL CAVITY FOLLOWING TOPICAL APPLICATION OF 5-AMINOLEVULINIC ACID

Background: The aim of photodynamic diagnosis (PDD) is the complete vi sualization of all neoplastic lesions in a tumorous organ after topica l or systemic application of a tumor selective photosensitizer. In thi s investigation we performed semiquantitative fluorescence measurement s following topical application of 5-aminolevulinic acid (5-ALA) in 11 patients with neoplastic lesions of the oral cavity. Methods: Time co urse and type of porphyrin accumulation were analyzed in neoplastic an d surrounding normal tissue by measuring emission spectra of 5-ALA-ind uced protoporphyrin IX (PpIX) fluorescence at regular intervals for up to three hours following 15 min continuous rinsing of a 0.4% 5-ALA so lution. After excitation with violet light of a high pressure xenon ar e lamp (375-440 nm), fluorescence images in the red spectral range fro m the tumor tissue and the corresponding macroscopic visible tumor wer e recorded with a CCD camera. A quantitative analysis of the fluoresce nce contrast in neoplastic and surrounding tissue was performed using an optical multichannel analyzer. Results: PpIX fluorescence was detec ted in the oral mucosa of all patients after local application of 5-AL A. PpIX in neoplastic tissue accumulated earlier in comparison to the surrounding normal tissue. The fluorescence contrast between tumor and host tissue was 10:1 and the maximum fluorescence was measured 1-2 ho urs following 5-ALA application. Conclusion: Labeling of mucosal lesio ns of the oral cavity with PpIX fluorescence induced by the local appl ication of 5-ALA seems to be a promising dignostic procedure for neopl astic lesions. Further investigations are required to assess the value of this new diagnostic procedure as a non-invasive and sensitive meth od for patients with head and neck cancer not only in pre- and postope rative diagnostic studies but also for a fluorescence-guided resection of tumors.