STEREOTACTIC RADIOTHERAPY FOR WET AGE-RELATED MACULAR DEGENERATION (INTREPID) Influence of Baseline Characteristics on Clinical Response

Purpose: To determine which patients respond best to stereotactic radiotherapy (SRT) for neovascular age-related macular degeneration. Methods: Participants (n = 230) receiving intravitreal anti-vascular endothelial growth factor injections for neovascular age-related macular degeneration enrolled in a randomized, double-masked sham-controlled trial comparing 16 Gray, 24 Gray, or Sham SRT. In a post hoc analysis, participants were grouped according to their baseline characteristics, to determine if these influenced SRT efficacy. Results: At 52 weeks, SRT was most effective for lesions <= 4 mm in greatest linear dimension and with a macular volume greater than the median value of 7.4 mm(3). For 26% of the participants with both these characteristics, SRT resulted in 55% fewer ranibizumab injections (2.08 vs. 4.60; P = 0.0002), a mean visual acuity change that was 5.33 letters superior to sham (+2.18 vs. -3.15 letters; P = 0.0284), and a 71.1-mu m greater reduction in mean central subfield thickness (-122.6 vs. -51.5 mm; P = 0.027). Other features associated with a positive response to SRT included pigment epithelial detachment and the absence of fibrosis. Conclusion: Stereotactic radiotherapy is most effective for neovascular age-related macular degeneration lesions that are actively leaking at the time of treatment, and no larger than the 4-mm treatment zone.