Determination of protoporphyrin IX distributions in skin tumors after the application of topical aminolevulinic acid

摘要

Abstract: Topical application of aminolevulinic acid (ALA) isknown to lead to enhanced concentrations ofprotoporphyrin IX (PpIX) in skin tumors versus normaltissue several hours after application. As PpIX is aneffective photosensitizer, topical ALA is being used inseveral clinical trials to treat skin malignancies,with variable success rates to date. As PpIX is highlyfluorescent, we have initiated a clinical trial todetermine the PpIX distribution in normal and tumortissue after the application of ALA via fluorescentimaging. Subjects apply ALA topically several hoursprior to surgical excision of basal cell carcinomas,and the resulting PpIX distributions in normal andtumor tissue are examined on a macroscopic andmicroscopic scale. This information allows us todetermine the exact degree of correlation between PpIXdistribution and tumor tissue, and gain insight intothe mechanism for the specificity of PpIX for tumortissue. In addition, we are exploring the possibilityof using the PpIX fluorescence as a guide to theexcision of skin tumors. !5