Author: Emmanuel Rebelo Neves (Portugal)
Co-authors: João Chaves, Paulo César Simões, Cristina Fonseca, Rui Proença, Joaquim Murta
The Collaborative Ocular Melanoma Study (COMS) trial helped establish the efficacy of plaque brachytherapy for the treatment of medium choroidal melanomas, allowing preservation of the globe and, to some extent, of visual acuity. Although local control of the tumor after plaque brachytherapy has excellent success rates, the exposure to radiation inevitably damages the surrounding ocular structures, especially vascular endothelium. Radiation retinopathy (RR) is the most frequent cause of visual loss following plaque brachytherapy and while its incidence may vary according to different centers, it can affect up to 42% of eyes within 5 years of treatment. Our center started treating patients with plaque brachytherapy nearly 8 years ago and is the only center with such expertise in Portugal. We aim to report the incidence of RR, as well as determine the predictors for its development in a group of patients submitted to plaque brachytherapy for the treatment of uveal melanoma (UM).
Ocular Oncology Reference Centre, Department of Ophthalmology, Coimbra University Hospital Centre, Portugal
Retrospective case series of patients consecutively submitted to plaque brachytherapy with I125 for the treatment of UM between November 2013 and October 2020. Patients with a follow-up of less than 3 months were excluded. We reviewed electronic and paper medical records for collection of demographic and clinical variables, as well as tumor variables. Categorical variables were reported as percentages and numerical variables as mean ± standard deviation (SD) or median (interquartile range, IQR) when normally distributed or skewed, respectively. The primary outcome of the study was the development of radiation retinopathy, defined by the presence of microaneurysms, cotton-wool spots, hard exudates, cystoid macular edema, vitreous hemorrhage, and retinal or iris neovascularization. Incidence rates were calculated with 95% Confidence Intervals [95% CI]. We used Cox Proportional Hazards models to identify statistically significant predictors for the development of radiation retinopathy.
We included 147 eyes of 147 patients. Mean age was 61.5 ± 13.4 years and 56.5% (n=83) were female. Median follow-up time was 24 (3-69) months. Choroidal melanomas comprised 89.8% (n=132) of the study sample, followed by the ciliary body melanomas (8.2%) and melanomas of both iris and ciliary body (2%). The incidence rate of radiation retinopathy was 27.7/100 person-years. The incidence rate of rubeosis iridis and neovascular glaucoma were 5.3 and 4.2/100 person-years, respectively. Local tumor control with plaque brachytherapy was achieved in 94.6% (n=137) of patients, while 5.4% (n=8) patients had to be submitted to secondary enucleation, 2 for therapy-resistant neovascular glaucoma and 6 for local tumor recurrence. On a stepwise multivariable model, higher initial tumor thickness (p<0.001) and peripapillary location (p=0.039) were positively associated with the outcome of radiation retinopathy, while higher patient age (p=0.039) and higher radiation dose to the lens (p<0.01) were inversely associated with it.
Concerning tumor control, our results display an excellent local tumor control rate after I125 plaque brachytherapy. Nevertheless, a considerable incidence rate of radiation retinopathy was apparent in our series. This study identified initial tumor thickness, peripapillary location, patient age and radiation dose to the lens as significant predictors for the development of RR.