Change in radiosensitivity with fractionated-dose irradiation of carbon-ion beams in five different human cell lines.
OBJECTIVE
To investigate the change in the surviving fractions by fractionated-dose irradiations with carbon ions, based on the recovery of potentially lethal damage (PLDR) and the change of radiosensitivity by every fractionated-dose irradiation.


METHODS
One normal human and four human-tumor cell lines were used. Cells were irradiated with carbon ions accelerated by the Heavy Ion Medical Accelerator in Chiba (HIMAC) at National Institute of Radiological Sciences in Japan. The LET values were estimated to be 13.18 keV/microm for low-LET beams and 76.92 +/- 0.20 keV/microm for high-LET beams. Fractionated-dose irradiations were carried out with 5 fractions within a 24-h interval.


RESULTS
The surviving fractions for the fractionated-dose irradiation with X-rays and carbon ions decreased exponentially with increasing the number of fractions in the tumor cell lines. In contrast, the surviving fractions for the carbon ions in normal human cells decreased exponentially as well as the tumor cell lines, while it tended to level off from the 3rd to the 5th fraction in the case of using X-rays.


CONCLUSIONS
The change in both the recovery ratio of the PLDR and radiosensitivity by every fractionated-dose irradiation depends on individual cell lines and the quality of radiations.
International Space Radiation Laboratory, National Institute of Radiological Sciences, Chiba, Japan. ms1251@columbia.edu
M
M
Suzuki
Y
Y
Kase
T
T
Kanai
K
K
Ando
D002244:Carbon / Q000627:therapeutic use*; D002470:Cell Survival / Q000502:physiology / Q000528:radiation effects*; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000502:physiology / Q000528:radiation effects; D063193:Heavy Ion Radiotherapy; D006801:Humans; D018499:Linear Energy Transfer; D011836:Radiation Tolerance / Q000502:physiology*; D011853:Radiobiology; D014407:Tumor Cells, Cultured / Q000502:physiology / Q000528:radiation effects; D014410:Tumor Stem Cell Assay
D002244:Carbon