Assessment of the homogeneous efficacy of carbon ions in the spread-out Bragg peak for human lung cancer cell lines.
OBJECTIVE
The aim of this study was to assess the radiosensitivities and homogeneous efficacy in the spread-out Bragg peak (SOBP) for lung cancer cell lines exposed to carbon ions.


METHODS
The dose-dependent survival rates of seven cell lines exposed to carbon ions, fast neutrons, and photons were obtained using colony-forming assays in vitro. The relative biological effectiveness (RBE) of carbon ions and fast neutrons to photons was determined by comparing the doses at the 10% and 1% survival levels.


RESULTS
The RBEs at 13, 40, 50, and 80 keV/microm were 1.20-1.29, 1.55-1.80, 1.57-2.00, and 1.69-2.58, respectively, at the 10% survival level. The RBE of 290 MeV carbon ions increased with increasing linear energy transfer. The biological dose (relative physical dose x RBE) distributions in the SOBP did not statistically differ at the proximal, mid, or distal points at the 10% (p = 0.945) and 1% (p = 0.211) survival levels, respectively; however, deviation of the biological dose at 10% and 1% survival were 3%-16% and 6%-24%, respectively. Furthermore, 290 MeV carbon ions at 80 keV/microm in the SOBP were nearly equivalent to 30 MeV fast neutrons.


CONCLUSIONS
Our results demonstrate nearly homogeneous effectiveness in the SOBP, although we are aware of the deviation in some cell lines.
Takiguchi
Yasuo
Y
Research Center Hospital for Charged Particle Therapy, National Institute of Radiological Sciences, Anagawa, 4-9-1, Inage-ku, Chiba, 263-8555, Japan. takiguchiyasuo@yahoo.co.jp
Miyamoto
Tadaaki
T
Nagao
Keiichi
K
Kuriyama
Takayuki
T
D002244:Carbon / Q000494:pharmacology*; D045744:Cell Line, Tumor / Q000528:radiation effects*; D002470:Cell Survival; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D011836:Radiation Tolerance; D013234:Stem Cells
D002244:Carbon