Stereotactic radiotherapy for treatment of subfoveal choroidal neovascularization in age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of visual loss among adults 65 years and older in western countries. Of patients with AMD who experience severe loss of vision, approximately 90% do so because of choroidal neovascularization (CNV). Visual loss is most severe when the CNV occurs directly under the fovea. Radiation-treated patients show some stabilization of visual acuity and reduction in extent of CNV compared to similar patients managed by observation alone. Various external beam radiation field arrangements were used to deliver the radiation treatments. The stereotactic radiation delivery technique employed in this study allows precise delivery of radiation to the target with much less radiation delivered to nearby sensitive structures (i.e., lens, optic nerves, optic chiasm, and contralateral eye). This aim of this paper is to describe our stereotactic technique for treatment of CNV, and the method we used for target definition and eye immobilization. We also compare the stereotactic technique with other techniques reported in the literature with regard to dose distributions, dose-volume histograms, and normal tissue complication probabilities (NTCP). We found that the position of the eye can be reproduced from one treatment fraction to the next, that the target can be localized accurately, and that stereotactic radiotherapy minimizes the dose to adjacent and surrounding normal structures while providing a homogeneous dose to the target area.