The biological effectiveness of antiproton irradiation.
OBJECTIVE
Antiprotons travel through tissue in a manner similar to that for protons until they reach the end of their range where they annihilate and deposit additional energy. This makes them potentially interesting for radiotherapy. The aim of this study was to conduct the first ever measurements of the biological effectiveness of antiprotons.


METHODS
V79 cells were suspended in a semi-solid matrix and irradiated with 46.7MeV antiprotons, 48MeV protons, or (60)Co gamma-rays. Clonogenic survival was determined as a function of depth along the particle beams. Dose and particle fluence response relationships were constructed from data in the plateau and Bragg peak regions of the beams and used to assess the biological effectiveness.


RESULTS
Due to uncertainties in antiproton dosimetry we defined a new term, called the biologically effective dose ratio (BEDR), which compares the response in a minimally spread out Bragg peak (SOBP) to that in the plateau as a function of particle fluence. This value was approximately 3.75 times larger for antiprotons than for protons. This increase arises due to the increased dose deposited in the Bragg peak by annihilation and because this dose has a higher relative biological effectiveness (RBE).


CONCLUSIONS
We have produced the first measurements of the biological consequences of antiproton irradiation. These data substantiate theoretical predictions of the biological effects of antiproton annihilation within the Bragg peak, and suggest antiprotons warrant further investigation.
Holzscheiter
Michael H
MH
Pbar Labs, LLC, Santa Fe, NM, USA.
Bassler
Niels
N
Agazaryan
Nzhde
N
Beyer
Gerd
G
Blackmore
Ewart
E
DeMarco
John J
JJ
Doser
Michael
M
Durand
Ralph E
RE
Hartley
Oliver
O
Iwamoto
Keisuke S
KS
Knudsen
Helge V
HV
Landua
Rolf
R
Maggiore
Carl
C
McBride
William H
WH
Møller
Søren Pape
SP
Petersen
Jørgen
J
Skarsgard
Lloyd D
LD
Smathers
James B
JB
Solberg
Timothy D
TD
Uggerhøj
Ulrik I
UI
Vranjes
Sanja
S
Withers
H Rodney
HR
Wong
Michelle
M
Wouters
Bradly G
BG
D000818:Animals; D002470:Cell Survival / Q000528:radiation effects*; D002478:Cells, Cultured / Q000528:radiation effects; D003037:Cobalt Radioisotopes; D003114:Colony-Forming Units Assay; D006224:Cricetinae; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D011522:Protons; D012062:Relative Biological Effectiveness
D003037:Cobalt Radioisotopes; D011522:Protons