Radiation retinopathy following plaque radiotherapy for posterior uveal melanoma

Objective: To identify the risk factors that lead to the development of rad iation retinopathy following plaque radiotherapy for posterior uveal melano ma. Radiation retinopathy is a slowly progressive, occlusive vasculopathy c haracterized by radiation-induced endothelial damage. Methods: Review of the medical records of patients with posterior uveal mel anoma treated with plaque radiotherapy. Results: Of 1300 patients with posterior uveal melanoma treated with plaque radiotherapy from July 1, 1976, through June 30, 1992, radiation retinopat hy developed in 560 (43.1%). By using Kaplan-Meier survival estimates, we f ound that 5% of the patients had nonproliferative radiation retinopathy at 1 year (95% confidence interval [CI], 3%-6%) and 42% at 5 years (95% CI, 38 %-45%). The proportion of patients with proliferative retinopathy was 1% at 1 year (95% CI, 0.2%-1.5%) and 8% at 5 years (95% CI, 5%-10%). Multivariat e analyses showed that the subset of clinical variables best related to the development of nonproliferative radiation retinopathy were tumor margin of less than 4 mm from foveola (P<.001), tumor limited to the choroid (P=.002 ), and radiation dose rate of greater than 260 cGy/h to the tumor base (P=. 02). The best subset of independent variables related to the development of radiation maculopathy were tumor of less than 4 mm to foveola (P<.001) and the use of radioisotope iridium 192 (Ir-192) (P=.02) compared with iodine 125 (I-125). From a multivariate model, the most important factors for the development of proliferative radiation retinopathy included diabetes mellit us (P=.01), radioisotope Ir-192 (P=.01) compared with I-125, and tumor base of greater than 10 mm (P=.02). Conclusions: Radiation retinopathy is a common finding after plaque radioth erapy for choroidal melanoma, occurring in 42% of patients at 5 years. The main predictors of radiation retinopathy are posterior tumor location with margin near the foveola and high radiation dose rate to the tumor base.