Hematoporphyrin phototherapy for experimental intraocular malignant melanoma.

Administration of a hematoporphyrin derivative (HpD) followed by photoradiation with red light completely or partially destroyed Greene hamster melanoma developed in the anterior chamber of rabbit eyes. Tumor-bearing eyes were divided into two groups. Twenty-two eyes received an HpD injection followed by exposure to red light from a slide projector with a 500-W quartz halogen lamp and a red filter (intensity to the tumor was about 4.0 mW/sq cm). In the control group (six eyes), eyes were exposed either to red light only or to HpD injection only. Local complications after therapy included edema and congestion of the conjunctiva, clouding of the cornea, and hemorrhage on the iris surface. The HpD itself has no cytotoxic effect, is preferentially retained in tumor cells, and causes a destructive photodynamic effect as a result of the production of cytotoxic singlet oxygen in the tumor. Accordingly, it may be a safe and potentially therapeutic procedure in the treatment of uveal melanoma.