2820 - Optic Nerve Dose and Long-Term Visual Outcomes for Uveal Melanoma Patients Treated with Eye Plaque Brachytherapy

Purpose/Objective(s): Eye plaque brachytherapy is the most common and effective treatment for Uveal Melanoma, allowing patients to avoid enucleation while providing excellent long term oncologic outcomes. Unfortunately, many patients will have decreased visual acuity from treatment. Our study aimed to determine if a relationship exists between long term visual acuity and dose along the optic nerve (ON), with the goal of improving treatment planning and optimizing long term visual outcomes in patients treated with eye plaque brachytherapy.

Materials/Methods: All patients treated at our institution for Uveal Melanoma with I-125 eye plaque brachytherapy to 85 Gy were eligible for our study. ON dosimetry was available starting in 2018 and dose to the ON was calculated at the optic disc and up to 3mm distally towards the brain (1 mm increments). Patients with this data were eligible if they had at least 12 months of follow up after treatment to allow maturation of possible visual deficits. 20/200 vision or worse is considered legal blindness. Univariate Cox proportional hazard models were used to evaluate the effect of radiation dose up to 3 mm along the ON on the risk of blindness.

Results: 118 patients, with 119 total eyes treated, had data available for visual acuity and dose to the optic nerve, of which 106 eyes at least 1 year of follow up for visual acuity. Median follow up was 2.55 years. 43 total eyes were permanently blinded, 8 of which were blind pre-treatment. Of the 35 patients blinded by treatment (36%), median time to blindness was 1.3 years. Mean dose at the optic disc for the 35 blinded eyes and the 63 un-blinded eyes was 57.35 Gy and 39.02 Gy respectively. Mean dose at 1mm, 2 mm and 3 mm along the optic verve was 25.29 Gy, 14.87 Gy and 10.14 Gy in the blinded eyes, respectively, while only 18.60 Gy, 11.22 Gy and 9.47 Gy in the unblinded eyes, respectively. Univariate analysis of dose at 0 mm, 1 mm, 2 mm and 3 mm leading to blindness revealed Hazard Ratios of 1.01, 1.03, 1.07 and 1.0 with p-values <0.001 for each, other than at 3 mm which had a p-value of .621.

Conclusion: Dose at the optic disc and along the ON may be correlated to long term blindness in patients with Uveal Melanoma treated with eye plaque brachytherapy. Additional dosimetric analysis can shed light on optimizing dose constraints to maintain long term visual acuity and help counsel patients on risks of legal blindness.