Radiobiological doses, tumor, and treatment features influence on outcomes after epiescleral brachytherapy. A 20-year retrospective analysis from a single-institution: part II

Purpose
To assess the influence of the radiobiological doses, tumor, and treatment features on retinopathy, cataracts, retinal detachment, optic neuropathy, vitreous hemorrhage, and neovascular glaucoma at the authors’ institution after brachytherapy for posterior uveal melanoma.

Material and methods
Medical records of 243 eyes with uveal melanoma, treated by iodine brachytherapy between 1996 and 2016 at a single center were analyzed. Clinical and radiotherapy data were extracted from a dedicated database. Biologically effective dose (BED) was included in survival analysis performed using Kaplan-Meier and Cox regressions. Relative survival rates were estimated, and univariate/multivariate regression models were constructed for predictive factors of each item. Hazard ratio and confidence interval at 95% were determined. Variables statistically significant were analyzed and compared by log-rank tests.

Results
The median follow-up was 73.9 months (range, 3-202 months). Cumulative probabilities of survival by Kaplan-Meier analysis at 3 and 5 years, respectively, were: 59% and 48% for retinopathy; 71% and 55% for cataracts; 63% and 57% for retinal detachment; 88% and 79% for optic neuropathy; 87% and 83% for vitreous hemorrhage; 92% and 89% for neovascular glaucoma, respectively. Using multivariate analysis, statistically significant risk factors were: age, tumor apical height, dose to foveola, and location of anterior border for retinopathy; age, dose to lens, type of plaque, and tumor shape, for cataracts; age, tumor apical height, and size of the plaque for retinal detachment; age, plaque shape, longest basal dimension, and BED to optic nerve for optic neuropathy; age, tumor apical height, and tumor shape for vitreous hemorrhage; tumor apical height and BED to foveola for neovascular glaucoma.

Conclusions
Tumor factors in addition to radiation treatment may contribute to secondary effects. Enhanced clinical optimization should evaluate radiobiological doses delivered to the tumor volume and surrounding normal ocular structures.