Plaque Radiotherapy for Posterior Uveal Melanoma (PUM) in 4000 Eyes in the Pre-Anti-VEGF Era: Impact of Radiation Dose to the Optic Disc and Foveola on ≥15-Letter Visual Acuity Loss

PURPOSE: To evaluate the impact of radiation dose to the optic disc and foveola on ≥15-letter visual acuity loss following plaque radiotherapy of posterior uveal melanoma (PUM) in the pre-anti-vascular endothelial growth factor (anti-VEGF) era. METHODS: We reviewed data on 4000 consecutive patients to assess radiation dose and dose rate to the optic disc and foveola on ≥15-letter visual acuity loss. RESULTS: The (median) patient age was 60 years, tumor diameter was 11.0 mm and thickness 4.5 mm, and distance to the optic disc was 4.0 mm and foveola 3.0 mm. The (median) dose (centiGray (cGy)) (dose rate (cGy/hour)) to the tumor apex was 8079 cGy (85 cGy/hour (cGy/hr)), to the optic disc was 3346 cGy (34 cGy/hr), and the foveola was 4021 cGy (40 cGy/hr). By Kaplan-Meier analysis, eyes that received ≤4000 cGy to optic disc developed ≥15-letter vision loss at 3 years with foveal dose 0-2000 cGy in 41%, 2001-4000 cGy in 60%, and 4001-6000 cGy in 68% (p<0.01). For eyes that received >4000 cGy to optic disc, ≥15-letter vision loss at 3 years was poorer (p nonsignificant). For those with optic disc dose ≤4000 cGy, a comparison (foveal dose 0-2000 versus (vs.) 2001-4000 cGy) led to hazard ratio (HR) of 1.71 (p<0.01) and (foveal dose 2001-4000 vs. 4001-6000 cGy) showed HR of 1.21 (p<0.03) for ≥15-letter vision loss. CONCLUSIONS: In the pre-anti-VEGF days, following treatment of PUM with plaque radiotherapy, higher radiation doses to the optic disc and foveola demonstrated greater ≥15-letter vision loss.