Early Peripapillary and Macular Microvascular Changes Following Ruthenium-106 Plaque Brachytherapy For Uveal Melanomas

Abstract

Objective: To evaluate early peripapillary and macular microvascular changes following ruthenium-106 (Ru-106) episcleral plaque brachytherapy for uveal melanoma using optical coherence tomography angiography (OCTA).

Design: Prospective case series.

Subjects: Twenty-four eyes of 24 patients with extramacular uveal melanoma treated with Ru-106 plaque brachytherapy at Cairo University Ocular Oncology Service.

Methods: All patients underwent ophthalmic evaluation and OCTA imaging at baseline, 3 months, and 6 months post-treatment.

Main outcome measures: Quantitative OCTA parameters included vessel density (VD) in the superficial (SCP), deep (DCP), and radial peripapillary capillary (RPC) plexuses, as well as foveal avascular zone (FAZ) area. Radiation doses to the tumor apex, fovea, and optic nerve were also recorded.

Results: Mean best-corrected visual acuity (BCVA) declined from 0.44 ± 0.30 logMAR at baseline to 0.78 ± 0.72 at 6 months (p = .028). Tumor height decreased significantly (p < .001). No clinical signs of radiation maculopathy or optic neuropathy were detected at 6 months. RPC density showed an early significant reduction (49.06 ± 2.77% to 44.95 ± 4.65% at 3 months, p < .001), with no further decline at 6 months; this loss was greater in tumors < 2 disc diameters from the optic disc. SCP showed localized reductions (46.23 ± 3.73% at baseline, 43.96 ± 5.15% at 3 months and 44.64 ± 4.26% at 6 months, p = .083). By contrast, DCP density declined progressively and diffusely (45.17 ± 4.86% to 44.90 ± 4.87% at 3 months and 42.23 ± 3.68% at 6 months, p = .017), accompanied by significant FAZ enlargement (0.25 ± 0.12 to 0.34 ± 0.11 mm², p < .001). Higher optic nerve radiation doses correlated with RPC loss (r = 0.492, p = .014) and poorer BCVA at 3 months (r=-0.454, p = .026) and 6 months (r=-0.412, p = .045), whereas macular doses showed no significant correlation. Tumor location influenced vascular response, with post-equatorial tumors showing greater DCP compromise, and pre-equatorial tumors exhibiting more SCP reduction. Systemic comorbidities did not significantly alter outcomes.

Conclusions: Ru-106 brachytherapy induces early, subclinical microvascular injury detecTable by OCTA. RPC changes are early and strongly correlate with optic nerve radiation dose and visual decline, SCP changes are localized, while DCP demonstrates progressive and generalized loss. Tumor location influenced injury patterns, reflecting differential radiation exposure. OCTA may serve as a noninvasive biomarker for early detection and risk stratification of radiation-induced microvascular injury.