Photodynamic therapy of pigmented choroidal melanomas

Abstract

Purpose: To evaluate the effectiveness of photodynamic therapy with chloroaluminum sulfonated phthalocyanine in the treatment of pigmented choroidal melanomas in a rabbit model.

Methods: Pigment containing B16F10 murine melanoma cells were implanted transclerally into the subchoroidal space of 28 immunosuppressed New Zealand albino rabbits. The animals were treated with daily injections of cyclosporine and were followed up until tumors at least 2 mm in height were detected by ultrasonography. Twenty-four hours after the intravenous injection of chloroaluminum sulfonated phthalocyanine (CASPc, 5 mg/kg), tumors were irradiated at 675 nm through an argon-pumped dye laser at estimated total light doses of 25 to 70 J/cm2. Control animals were treated with light only or photosensitizer only. The animals were followed up for 4 1/2 to 8 weeks with regular fundus examinations.

Results: Twenty tumor-bearing rabbits were treated with light and dye. The tumor regressed in 12 animals. Five of these animals were followed up for at least 4 1/2 weeks and the other seven for 8 weeks after treatment. At light doses under 40 J/cm2, tumor regrowth was observed in five animals within 10 days of treatment. In all control groups, the tumor-bearing eyes were filled with tumor cells by the third week after implantation. Histologic examination of tumors treated with photosensitizer and light revealed prominent vascular damage early after treatment that resulted in vascular occlusion. Tumor necrosis was evident within 24 hours of treatment.

Conclusions: Results suggest that photodynamic therapy may have a role in the treatment of pigmented choroidal melanomas.