PHOTODYNAMIC THERAPY OF EXPERIMENTAL CHOROIDAL MELANOMA USING LIPOPROTEIN-DELIVERED BENZOPORPHYRIN

Background: Benzoporphyrin derivative monoacid (BPD) is a new photosen sitizer currently undergoing clinical trial for cutaneous malignancies . Compared with the clinically most frequently used sensitizer, Photof rin, BPD may offer higher tumor phototoxicity, better tissue penetrati on, and absence of significant skin sensitization. Low-density lipopro tein (LDL) carriers heighten efficiency and selectivity of BPD because neovascular and tumor cells express an increased number of LBL recept ors. Hence, in addition to the vaso-occlusive effects similar to most other photosensitizers, LDL-BPD also has been shown to cause direct tu mor cell damage. Methods: Benzoporphyrin derivative monoacid was compl exed with human LDL and used in photodynamic treatment of choroidal me lanomas experimentally induced in eight albino rabbits. Five rabbits s erved as controls. Three hours after intravenous injection of 2 mg/kg body weight of LDL-BPD, eight tumors were irradiated at 692 nm and 100 J/cm(2) via an argon-pumped dye laser coupled into a slit lamp. Resul ts: Angiography and histologic findings showed immediate photothrombos is after disintegration of endothelial membranes. After complete necro sis of tumor cells within 24 hours, a small fibrotic scar slowly devel oped. No tumor regrowth was noted up to 6 weeks when animals were kill ed. Conclusion: These data suggest that photodynamic treatment with LD L-BPD may be a promising modality for multiple clinical applications, including tumors and neovascularizations II.