Carbon ion therapy for ocular melanoma: planning orthogonal two-port treatment.

We recently started orthogonal two-port carbon ion therapy for choroidal melanoma with the intent to reduce the incidence of radiation complications that occur with mono-port therapy. Treatment planning techniques involving therapeutic beam characteristics are described here. The vertical (140 MeV/u) and horizontal (170 MeV/u) carbon ion beams from the synchrotron at the NIRS were shaped, using the passive beam delivery system, to irradiate the target volume. The range modulating ridge filters were designed to produce spread-out Bragg peaks (SOBPs) with a region of uniform HMV-I cell killing. The apertures and range compensators were designed for individual patients. A commercial treatment planning system, which was customized to our general carbon ion therapy, was tested for applicability to this treatment. Dose distributions were calculated with either a broad beam or a pencil beam algorithm using parameters determined by measurements and calculations. We evaluated the accuracy of the system software features, and replaced or added some other features to the software. The system was used for 12 patients during the past year. For nine patients two-port treatment was assessed to be more effective than mono-port therapy and these patients were treated with two fractions of vertical beams and three fractions of horizontal beams.

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 > or =50 GyE to iris-ciliary body) (p = 0.002) and ODI (p = 0.036). The 3-year NVG rate for patients with V50IC > or =0.127 mL and those with V50IC <0.127 mL were 71.4 +/- 8.5% and 11.5 +/- 6.3%, respectively. The corresponding rate for the patients with and without ODI were 62.9 +/- 10.4% and 28.4 +/- 8.0%, respectively. CONCLUSION: Dose-volume histogram analysis with computed tomography indicated that V50IC and ODI were independent risk factors for NVG. An irradiation system that can reduce the dose to both the anterior segment and the optic disk might be worth adopting to investigate whether or not incidence of NVG can be decreased with it.