[Optimization of irradiation time in the treatment of malignant melanoma of the choroid with beta applicators (106Ru/106Rh)].

Brachytherapy with 106Ru/106Rh necessitates protracted irradiation because the applicators have to be sutured to the sclera. Protracted radiotherapy causes more intensive damage in tumor cells with increased metabolism and a higher mitosis rate than in normal tissue. Beta irradiation of rabbit eyes with 0.258-0.231 Gy/min produced more extensive exudative reactions and morphological damage of the retina than a lower dosage rate with 0.035-0.026 Gy/min and the same total dose of 650 Gy. For the study reported here 75 patients suffering from choroidal melanoma and irradiated with 106Ru/106Rh plaques between 1967 and 1977 were evaluated. They developed more exudative and hemorrhagic side effects after a short period of irradiation (1-6 days) than after a longer one (7-14 days). Spontaneous recovery of the radiation-induced retinal detachment was seen in all cases. Complete tumor regression with development of a flat scar was achieved with almost equal success with both short-term and protracted irradiation. To minimize radiogenic side effects the duration of irradiation recommended hitherto, i.e., 7-14 days, should be adhered to when treating malignant melanomas of the choroid with beta-ray applicators.