19. Difference among Heavy Ion Beams in Cell Killing and Mutation Induction

Yoshiya Furusawa, Tatsuaki Kanai, Naoyuki Shigematsu¹, Noriko Ihara¹, Tetsuya Kawata¹, Osamu Kawaguchi¹, Atsuya Takeda¹, Ryoichi Ishibashi¹, Shoji Kutsuki¹, Atsushi Kubo¹, Koichi Isobe², Takashi Uno² and Hisao Ito²
(¹Keio Univ.; ²Chiba Univ.)

Keywords: cell killing, mutations, heavy ion beam

In this study, human cancer cell lines were used to attempt to clarify the radiobiological effects of heavy ion beams on carbon beam radiotherapy. Killing efficiency was determined by the usual colony forming method, and mutation was observed as the induction of 6-thioguanine resistant colony. Cells were irradiated by HIMAC carbon ion beams with LET value at 20 or 80 keV/µm, or neon ion beams at 80 keV/µm. Carbon beams of 80 keV/µm had an enhanced cytotoxic effect compared with those of 20 keV/µm. The carbon beams of 80 keV/µm showed almost the same efficiency in cell killing compared with neon beams even though they had the same LET value. Efficiencies of induction of mutation for all heavy ion beams tested were significantly higher than that for X-rays for all cell lines used. The efficiency for 80 keV/µm carbon beams was higher than that for 20 keV/µm beams. The efficiency was, however, lower for neon ion beams then carbon beams at 80 keV/µm, even though they had the same LET value. Split dose irradiation of carbon beams showed no effect on cell killing but the mutation efficiency was lowered. Neon beams might be more appropriate for cancer therapy with heavy ion beams, and the fractionated dose might be appropriate to reduce the mutation frequency in heavy ion radiotherapy.

Publications:
Shigematsu, N., Ihara, N., Kawata, T., Kawaguchi, O., Takeda, A., Ishibashi, R., Kutsuki, S., Kubo, A., Kanai, T., Furusawa Y., Isobe, K., Uno, T., and Ito, H.: Int. J. Mol. Med. 7, 509-513, 2001.