A comparison of biological effects of modulated carbon-ions and fast neutrons in human osteosarcoma cells.
OBJECTIVE
To compare the biological effects of a 135 MeV/u carbon-ion beam and 13 MeV fast neutron beam using human osteosarcoma cells.


METHODS
We have studied the clonogenic cell survival, recovery of potentially lethal damage (PLD) in plateau phase cells, and spheroid cure in multicellular spheroid after irradiation at various positions in the plateau and spread out Bragg peak (SOBP) of a 135 MeV/u carbon-ion beam and with 13 MeV neutrons. The carbon beam had a 4-cm range in water and a range filter was used to produce a 3-cm extended-peak region. The reference radiation was 137Cs gamma-rays.


RESULTS
The relative biological effectiveness (RBE) values for 10% survival level of plateau phase cells for carbon-ions at the position of plateau, proximal peak, midpeak, and distal peak within the SOBP, and neutrons were 1.71, 2.48, 2.63, 3.47, and 2.29, respectively. Corresponding RBE values at 1% level were 1.64, 1.93, 2.06, 2.49, and 2.05. The extent of recovery from PLD was reduced after carbon-ions at proximal peak, midpeak, and distal peak, and neutrons, although not substantially reduced after carbon-ions at plateau. The RBE values for 50% spheroid cure level of spheroids for carbon-ions at the position of plateau, proximal peak, midproximal peak, middistal peak, and distal peak within the SOBP, and neutrons were 1.69, 1.88, 1.87, 1.94, 2.03, and 1.90, respectively.


CONCLUSIONS
The biological parameters measured all indicate an approximately comparable biological effectiveness between 75-80 KeV/microns carbon-ions of the SOBP and 13 MeV neutrons in the human tumor model studied in vitro.
Kubota
N
N
Department of Radiology, Yokohama City University School of Medicine, Japan.
Suzuki
M
M
Furusawa
Y
Y
Ando
K
K
Koike
S
S
Kanai
T
T
Yatagai
F
F
Ohmura
M
M
Tatsuzaki
H
H
Matsubara
S
S
D002244:Carbon / Q000627:therapeutic use*; D002470:Cell Survival; D004260:DNA Repair; D006801:Humans; D009502:Neutrons / Q000627:therapeutic use*; D012516:Osteosarcoma / Q000532:radiotherapy*; D012062:Relative Biological Effectiveness; D014407:Tumor Cells, Cultured
D002244:Carbon