External beam radiotherapy in exudative age-related macular degeneration: a pooled analysis of Phase I data

In recent years external beam radiotherapy (EBRT) has been proposed as a tr eatment for the wet form of age-related macular degeneration (AMD) where ch oroidal neovascularization (CNV) is the hallmark. While the majority of pil ot (Phase I) studies have reported encouraging results, a few have found no benefit, i.e. EBRT was not found to result in either improvement or stabil ization of visual acuity of the treated eye. The natural history of visual loss in untreated CNV of AMD is highly variable. Loss of vision is influenc ed mainly by the presenting acuity, and size and composition of the lesion, and to a lesser extent by a variety of other factors. Thus the variable ou tcome reported by the small Phase I studies of EBRT published to date may s imply reflect the variation in baseline factors. We therefore obtained info rmation on 409 patients treated with EBRT from eight independent centres, w hich included details of visual acuity at baseline and at subsequent follow -up visits. Analysis of the data showed that 22.5% and 14.9% of EBRT-treate d eyes developed moderate and severe loss of vision, respectively, during a n average followup of 13 months. Initial visual acuity, which explained 20. 5% of the variation in visual loss, was the most important baseline factor studied. Statistically significant differences in loss of vision were obser ved between centres, after considering the effects of case mix factors. Com parisons with historical data suggested that while moderate visual loss was similar to that of the natural history of the disease, the likelihood of s uffering severe visual loss was halved. However, the benefit in terms of ma intained/improved vision in the treated eye was modest.