V-79 Chinese hamster cells irradiated with antiprotons, a study of peripheral damage due to medium and long range components of the annihilation radiation.
OBJECTIVE
Radiotherapy of cancer carries a perceived risk of inducing secondary cancer and other damage due to dose delivered to normal tissue. While expectedly small, this risk must be carefully analysed for all modalities. Especially in the use of exotic particles like pions and antiprotons, which annihilate and produce a mixed radiation field when interacting with normal matter nuclei, the biological effective dose far out of field needs to be considered in evaluating this approach. We describe first biological measurements to address the concern that medium and long range annihilation products may produce a significant background dose and reverse any benefits of higher biological dose in the target area.


METHODS
Using the Antiproton Decelerator (AD) at CERN (Conseil Européen pour la Recherche Nucléaire) we irradiated V-79 Chinese Hamster cells embedded in gelatine using an antiproton beam with fluence ranging from 4.5 x 10(8) to 4.5 x 10(9) particles, and evaluated the biological effect on cells located distal to the Bragg peak using clonogenic survival and the COMET assay.


RESULTS
Both methods show a substantial biological effect on the cells in the entrance channel and the Bragg Peak area, but any damage is reduced to levels well below the effect in the entrance channel 15 mm distal to the Bragg peak for even the highest particle fluence used.


CONCLUSIONS
The annihilation radiation generated by antiprotons stopping in biological targets causes an increase of the penumbra of the beam but the effect rapidly decreases with distance from the target volume. No major increase in the biological effect is found in the far field outside of the primary beam.
Kovacevic
Sandra
S
University of Montenegro, Podgorica, Montenegro.
Bassler
Niels
N
Hartley
Oliver
O
Knudsen
Helge
H
Vranjes
Sanja
S
Garaj-Vrhovac
Vera
V
Holzscheiter
Michael
M
D000818:Animals; D016466:CHO Cells; D002470:Cell Survival / Q000528:radiation effects; D003114:Colony-Forming Units Assay; D020552:Comet Assay; D006224:Cricetinae; D003412:Cricetulus; D004249:DNA Damage; D011522:Protons; D011829:Radiation Dosage; D011836:Radiation Tolerance
D011522:Protons