Presentation The effect of uneven fractionation using high LET carbon-ion beams for tumor metastatic abilities

松本, 孔貴  ,  山下, 慶  ,  李, 恵子  ,  平山, 亮一  ,  鵜澤, 玲子  ,  安藤, 興一  ,  増永, 慎一郎  ,  古澤, 佳也  ,  坪井, 康次  ,  櫻井, 英幸

In recent years, the tumor local control after radiotherapy has been improvement due to the widespread of the particle beam therapy, IMRT etc.. However, the patients’ survival is not satisfied because of the recurrence or distant metastasis. Hyperfractionation is the mainstream of the recent radiotherapy, however, our previous study showed low-dose of lo-LET radiation have a potential to enhance the metastatic abilities. The aim of this study is to examine the effect of uneven fractionation for cell survival and metastatic potential. Highly metastatic LM8 cells were irradiated with uneven fractionated carbon-ion beams (C-ions) at 24 h interval. X-rays were used as a reference beam in the radiobiological effect. Cells were irradiated by 2 fraction (fr.) and multicellular spheroids were irradiated by 5 fr. with the same total dose but different dose allocation (Table 1). The initial high dose group showed strongest biological effect, whereas the effect of last only high dose group was weakest and weaker as compared with the even fractionation. The effects of initial high dose were more significant in the metastasis suppression. After the C-ions uneven fractionation, the difference of the biological effects among the uneven fractionation schemes was extremely small in terms of metastasis suppression and cell killing. It is suggested that uneven fractionation using the high dose and/or high-LET beams as the initial irradiation suppressed efficiently the cell survival and metastatic potential compared with even fractionation and the uneven fractionation may effective from viewpoint of the suppression of tumor metastasis.
55th PTCOG

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