Abstract
Abstract: :
Purpose: Uveal melanomas are the most common primary intraocular malignant tumor in adults. The purpose of this study was to evaluate the effect of hyper-accelerated carbon ion irradiation on uveal melanoma cells in vitro. Methods: Two cell lines obtained from human primary uveal melanomas (92-1, OCM-1) and one cell line obtained from human metastatic uveal melanoma (OMM-1) were used (kindly provided by Dr. HMH Hurks and Dr. MJ Jager, Department of Ophthalmology, Leiden University Medical Center, The Netherland). The irradiation by carbon ions was performed at the Heavy Ion Medical Accelerator in Chiba (HIMAC) of the National Institute of Radiological Science, Japan. The energy of carbon ions were 290 MeV/u, the spread out Bragg peak was 6 cm, and mean linear energy transfer was 50 keV/µm. Six different doses of carbon ions, 0.6, 1.5, 2.5, 3.5, 4.5 and 6.0 Gy were used. For control, we irradiated X-ray(200 kVp, 20mA, 1Gy/min) to the same type of cells with 6 different doses, 1.5, 3.0, 4.5, 6.5, 8.0 and 9.0 Gy. After irradiation, the survival ratios of the cells were calculated by clonogenic survival determination. Results: Both carbon ion radiation and X-ray radiation caused a dose-dependent reduction in cell survival. In the 92-1 cell line, the D10, (0.1 cell surviving level) was 2.0 Gy for X-ray and 1.8 Gy for carbon ion. In both OCM-1 and OMM-1, D10 was about 6.2 Gy and 4.0 Gy, respectively. Conclusions: The relative biological effectiveness (RBE) of carbon ion irradiation is greater than 1.0 compared with X-ray for choroidal melanoma cells. RBE is higher for those cells with low radiosensitivity.
Keywords: melanoma • radiation therapy