Phase I/II study of proton beam irradiation for the treatment of subfoveal choroidal neovascularization in age-related macular degeneration: treatment techniques and preliminary results

Age-related macular degeneration is the prevalent etiology of subfoveal choroidal neovascularization (CNV). The only effective treatment is laser photocoagulation, which is associated with decreased visual acuity following treatment in most patients. This study assessed both the response of subfoveal CNV to proton beam irradiation and treatment-related morbidity. We evaluated preliminary results in patients treated with an initial dose of 8 Cobalt Gray Equivalents (CGE) using a relative biological effectiveness (RBE) of 1.1. Twenty-one patients with subfoveal CNV received proton irradiation to the central macula with a single fraction of 8 CGE; 19 were eligible for evaluation. Treatment-related morbidity was based on Radiation Therapy Oncology Group (RTOG) criteria; response was evaluated by Macular Photocoagulation Study (MPS) guidelines. Fluorescein angiography was performed; visual acuity, contrast sensitivity, and reading speed were measured at study entry and at 3-month intervals after treatment. Follow-up ranged from 6 to 15 months. No measurable treatment-related morbidity was seen during or after treatment. Of 19 patients evaluated at 6 months, fluorescein angiography demonstrated treatment response in 10 (53%); 14 (74%) patients had improved or stable visual acuity. With a mean follow-up of 11.6 months, 11 (58%) patients have demonstrated improved or stable visual acuity. A macular dose of 8 CGE yielded no measurable treatment morbidity in patients studied. Fluorescein angiography demonstrated that regressed or stabilized lesions were associated with improved visual acuity as compared with MPS results. In the next phase, a dose of 14 CGE in a single fraction will be used to further define the optimal dose fractionation schedule.