Risk factors for neovascular glaucoma after carbon ion radiotherapy of choroidal melanoma using dose–volume histogram analysis

Purpose: To determine the risk factors for neovascular glaucoma (NVG) after carbon ion radiotherapy (C-ion RT) of choroidal melanoma. Methods and Materials: A total of 55 patients with choroidal melanoma were treated between 2001 and 2005 with C-ion RT based on computed tomography treatment planning. All patients had a tumor of large size or one located close to the optic disk. Univariate and multivariate analyses were performed to identify the risk factors of NVG for the following parameters; gender, age, dose–volumes of the iris-ciliary body and the wall of eyeball, and irradiation of the optic disk (ODI). Results: Neovascular glaucoma occurred in 23 patients and the 3-year cumulative NVG rate was 42.6 ± 6.8% (standard error), but enucleation from NVG was performed in only three eyes. Multivariate analysis revealed that the significant risk factors for NVG were V50IC (volume irradiated ≥50 GyE to iris-ciliary body) ( p = 0.002) and ODI ( p = 0.036). The 3-year NVG rate for patients with V50IC ≥0.127 mL and those with V50IC