Proton irradiation of malignant uveal melanoma. A five year follow-up of patients treated in Uppsala, Sweden.

Twenty patients with malignant uveal melanoma were treated at the The Svedbergh cyclotron in Uppsala from 1989 to 1991. Each tumour received a total dose of 54.6 Gy in four equal fractions on four following days. After treatment the melanoma in all eyes showed decrease in size combined with irradiation retinopathy. In eight patients the treatment was successful after five years. Nine eyes had to be enucleated, two due to recurrence and seven due to neovascular glaucoma. Three patients died, two from metastases and one from heart disease. In all patients the visual acuity was dependent on the distance between the irradiation field and the macula or optic nerve. Each patient suffered from transient post irradiation skin erythema and permanent loss of eyelashes and eyebrows when these were included in the irradiation field. The development of secondary glaucoma was positively correlated with tumour volume, but not to the age or sex of the patients. Histological examination of all the enucleated eyes revealed residual viable tumour without obvious radiation damage: mitotic figures were not identified. MRI examination, performed before and after treatment, demonstrated a marked shift in water binding properties after irradiation. The final visual acuity was dependent on the location of the tumour.