Transscleral laser thermotherapy of hamster Greene melanoma: inducing tumour necrosis without scleral damage

The feasibility of using transscleral thermotherapy (TSTT) to induce necros is of choroidal melanoma without causing damage to the sclera was investiga ted. Fifty-two subcutaneously implanted hamster melanomas covered by human donor sclera were irradiated for 1 min with an 810 nm laser using a 3 mm sp ot diameter, with and without cooling of the scleral surface. Immediately a fter irradiation the temperature of the scleral surface was measured with a n infrared camera. Irradiation at 2000 mW, without cooling of the sclera, r esulted in tumour necrosis to a mean depth of 4.4 mm and a mean diameter of 5.5 mm, without causing damage to the scleral collagen; the surface temper ature of the sclera was 44.5 degreesC, and the estimated temperature at the sclera-tumour interface was 60.1 degreesC. There was a sharp demarcation b etween the viable and the necrotic part of the tumour. TSTT at 2500 mW, wit hout cooling of the sclera, caused maximal tumour necrosis to a mean depth of 5.2 mm and a mean diameter of 5.9 mm; the scleral layers adjacent to the tumour had an estimated temperature of 67.6 degreesC and showed signs of d amage in 14% of the experiments. Cooling of the sclera resulted in less the rmal damage to the sclera but also less tumour necrosis. Results indicate t hat TSTT has potential in the treatment of choroidal melanoma. (C) 2001 Lip pincott Williams & Wilkins.