27. Time-Course of Reoxygenation in Experimental Murine Tumors after Carbon-Beam and X-Ray Irradiation
Sachiko Koike, Kumie Nojima,
Yoshiya Furusawa, Koichi Ando,
Natsuo Oya1, Keisuke Sasai1,
Toru Shibata1, Takehisa Takagi1,
Keiko Shibuya1 and Masahiro Hiraoka1
(1Kyoto Univ.)
Keywords: high-LET radiation, reoxygenation, SCCVII, EMT6
We compared the tumor reoxyge nation patterns in three different murine tumor cell lines after X-ray irradiation with those after carbon beam irradiation using the heavy ion medical accelerator (HIMAC) system. The tumors of the cell lines SCCVII, SCCVII-variant-1 and EMT6 on the hind legs of mice received local priming irradiation with a carbon beam (8 Gy, 73 keV/ µm in LET, 290 MeV/u, 6 cm SOBP) or X-rays (13 Gy, 250 kVp). After various intervals, the mice were given whole-body test irradiation (16 Gy, 250 kVp X-rays) either in air or after they were killed. The hypoxic fractions were estimated as the proportions of the surviving fractions of the tumors in killed mice to those in air-breathing mice. In the SCCVII tumors, the hypoxic fractions at 0.5 h were 50% and 21% (p < 0.01), and 21% and 31% at 24 h after X-ray irradiation and after carbon beam irradiation, respectively. In the EMT6 tumors, the reoxygenation patterns after X-irradiation and carbon beam irradiation were similar. We concluded that the reoxygenation pattern differed among the three tumor cell lines, and that reoxygenation tended to occur more rapidly after carbon beam irradiation than after X-ray irradiation for SCCVII and SCCVII-variant-1 tumors.
Publications:
Oya, N., Sasai, K., Shibata, T., Takagi, T., Shibuya, K., Koike, S,. Nojima, K., Furusawa, Y., Ando, K., and Hiraoka, M.: J. Radiat. Res. 42, 131-141, 2001.