INTERSTITIAL PHOTODYNAMIC THERAPY IN THE CANINE PROSTATE WITH DISULFONATED ALUMINUM PHTHALOCYANINE AND 5-AMINOLEVULINIC ACID-INDUCED PROTOPORPHYRIN-IX

BACKGROUND. Photodynamic therapy (PDT) is an experimental approach for treating prostate cancer localized to the gland that does not involve surgery or irradiation. Second-generation photosensitizers 5-aminolev ulinic acid (ALA) and aluminum disulfonated phthalocyanine (AlS2Pc) we re studied in the normal canine prostate. METHODS. Tissue biodistribut ion of photosensitizers on serial biopsies was examined using fluoresc ence microscopy. Photodynamic therapy was done by delivering red light interstitially at 100 mW through fibers placed under transrectal ultr asound guidance. RESULTS. Peak levels of AlS2Pc appeared at 5-24 hr an d at 3 hr for ALA. Macroscopic PDT lesions were up to 12 mm in diamete r using AlS2Pc, but only 1-2 mm with ALA. Light at 300 mW caused therm al lesions. At 28 days, damaged glands remained atrophic, but the inte rlobular supporting stroma was well-preserved. Urethral lesions healed by 28 days without functional impairment. CONCLUSIONS. Although the r esults with ALA were disappointing, PDT using AlS2Pc looks like a prom ising modality for treatment of localized prostate cancer. (C) 1997 Wi ley-Liss, Inc.