Analysis of Vascular Changes after Proton Irradiation using OCT-A in Patients with Uveal Melanoma

Abstract

Purpose : To evaluate changes in macular vasculature within 2 disc diameters (DD) of the fovea using optical coherence tomography angiography (OCT-A) after proton beam irradiation (PBI) in patients with uveal melanoma.

Methods : This cross-sectional study included patients with small-medium tumors (height ≤5mm and largest basal diameter ≤15mm) located within 2DD of the fovea or optic disc who completed OCT-A scans after PBI. The majority (53.8%) of post-treatment OCT-A scans were completed within 3 years (±6 months) after treatment (mean time from PBI to OCT-A: 3.5 years; range: 2.1 - 7.0 years). Patients with tumors abutting the optic disc and involving the fovea were excluded. Automated measures of vessel density (VD) in both the superficial capillary plexus (SCP) and the deep capillary plexus (DCP) in the parafoveal area (area measuring 3 mm around fovea) were obtained using the built-in angioanalytics software on the Optovue Avanti. Radiation dose to the fovea was obtained using treatment planning software (EyePlan version 3.06). Spearman correlation coefficient and Wilcoxon rank-sum test were used to evaluate relationships between tumor location, radiation dose, vascular changes and visual acuity (VA).

Results : Thirteen patients (62% male; median age: 65.5 years) were included in this study; 10 (77%) had tumors located within 2 DD of the fovea and 9 (69.2%) had baseline visual acuity (VA) of 20/40 or better. The mean SCP VD in the parafoveal region for tumors located within 2DD of the fovea was 37.7% compared to 47.4% for tumors further away from the fovea (P=.01). Differences in mean DCP VD in this region were not significantly different (42.5% vs. 46.8% for tumors <2DD and > 2DD from fovea respectively, P=.50). Median radiation dose to the fovea was 46 Gy (RBE), and inversely related to both SCP VD (r=-.89, P<.001) and DCP VD (r=-.53, P=.06). There was a trend toward reduced SCP VD in those with worse VA compared to those with VA of 20/40 or better (34.4% v. 42.6%, P=.08).

Conclusions : These data suggest that tumors in close proximity to the fovea and high foveal radiation dose are associated with decreased VD in both the superficial capillary plexus and deep capillary plexus in the parafoveal region of the retina. Larger studies are needed to further explore the relationship between these OCT-A metrics and vision loss after radiation therapy.

This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.