[Br-76]Bromodeoxyuridine, a potential tracer for the measurement of cell proliferation by positron emission tomography, in vitro and in vivo studies in mice
Je. Ryser et al., [Br-76]Bromodeoxyuridine, a potential tracer for the measurement of cell proliferation by positron emission tomography, in vitro and in vivo studies in mice, NUCL MED BI, 26(6), 1999, pp. 673-679
5-Bromo-2'-deoxyuridine (BrUdR) labeled with Br-77 and Br-76 was compared w
ith 5-iodo-2'-deoxyuridine (IUdR) labeled with I-125 Or I-131, first in vit
ro then in in vivo experiments in mice. The results showed a significantly
higher incorporation of BrUdR into DNA than IUdR, which can be explained by
the greater similarity (size and surface hydrophilicity of the molecules)
of BrUdR to thymidine. Both tracers are dehalogenated quickly in vivo but n
ot in vitro. Free bromide is excreted more slowly than iodide, resulting in
a higher background activity level after the application of [Br-76]BrUdR a
nd compensates for the favorable DNA incorporation. Br-76 has more favorabl
e properties than I-124 for imaging purposes with positron emission tomogra
phy (PET) because of a very convenient half-life (16 h vs. 4.15 days) and a
bout double the positron yield per decay, However, the more favorable physi
cal properties are balanced by the slower excretion and thus the estimated
radiation dose is higher in the case of Br-76 than I-124. Thus, both tracer
s, [I-124]IUdR and [Br-76]BrUdR are potentially suitable but not optimal to
measure cell proliferation in vivo. The difference between the two tracers
is small and the extrapolation from mice to human difficult, and thus it c
annot be concluded if one of the tracers would be better than the other for
imaging of cancer patients. NUCL MED BIOL 26;6:673-679, 1999. (C) 1999 Els
evier Science Inc. All rights reserved.