Neuroretinal inflammatory biomarkers anticipating radiation-induced macular edema

Author: Raffaele Parrozzani (Italy)

Co-authors: Luisa Frizziero, Giulia Midena, Giulia Marchione, Elisabetta Pilotto, Edoardo Midena

Purpose

To evaluate, using spectral domain optical coherence tomography (SD-OCT), the presence of hyper-reflective retinal spots (HRS) as an early imaging biomarker anticipating the development of radiation induced macular edema (ME) in patients treated by Iodine-125 (I-125) brachytherapy because affected by posterior uveal melanoma (UM).

Setting/Venue

Institutional, observational, cross-sectional study with prospective enrollment.

Methods

Thirty eyes of 30 patients scheduled for I-125 brachytherapy for a primary uveal melanoma without posterior pole involvement by the tumor and/or macular involvement in the irradiation field were prospectively enrolled. Patients were followed every 3 months for 5 years from brachytherapy. All subjects underwent full ophthalmologic examination, including macular SD-OCT, even in en face modality. HRS were localized and measured both in the inner and outer retina by two independent masked graders. HRS were defined as discrete intraretinal reflectivity changes ≤30 μm, characterized by reflectivity similar to nerve fiber layer and absence of back shadowing.

Results

Seventeen patients developed ME at a mean time of 24.2 months (±15.1) (group 1). No evidence of ME was identified in 13 patients at 5-year follow-up (group 2). HRS significantly increased in number in group 1 patients between baseline and the last visit before the evidence of ME, both in the inner (p=0.005) and outer retina (p<0.05). HRS increased in number in group 2 patients between baseline and the last 5-year follow-up visit without reaching statistical significance (p>0.05). In group 1, the number of HRS spot at last follow-up before the evidence of ME was statistically related to the OCT central subfield thickness at ME appearance (P =0.05). The intergrader agreement was at least substantial for all HRS measurements (ICC=0 .80).

Conlusions

SD-OCT documents early discrete intraretinal reflectivity changes (HRS) in eyes treated with eye irradiation. HRS significantly increase in number in patients developing ME, even 6 months before the evidence of ME. HRS could be considered as an early clinical biomarker of intraretinal inflammation in patients treated with eye irradiation, anticipating radiation-induced ME.