RT Journal Article
SR Electronic
T1 Targeting of Osseous Sites with α-Emitting <sup>223</sup>Ra: Comparison with the β-Emitter <sup>89</sup>Sr in Mice
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 252
OP 259
VO 44
IS 2
A1 Gjermund Henriksen
A1 Darrell R. Fisher
A1 John C. Roeske
A1 Øyvind S. Bruland
A1 Roy H. Larsen
YR 2003
UL http://jnm.snmjournals.org/content/44/2/252.abstract
AB The bone-seeking property and the potential exposure of red marrow by the α-particle emitter 223Ra (half-life, 11.43 d) were compared with those of the β-emitter 89Sr (half-life, 50.53 d). Methods: The biodistributions of 223Ra and 89Sr were studied in mice. Tissue uptake was determined at 1 h, 6 h, 1 d, 3 d, and 14 d after intravenous administration. Radiation absorbed doses were calculated for soft tissues and for bone. Multicellular-level doses were estimated for bone marrow cavities. Results: Both 89Sr and 223Ra selectively concentrated on bone surfaces relative to soft tissues. The measured bone uptake of 223Ra was slightly higher than that of 89Sr. At 24 h, the femur uptake of 223Ra was 40.1% ± 7.7% of the administered activity per gram of tissue. The uptake in spleen and most other soft tissues was higher for 223Ra than for 89Sr. Although predominant clearance of 223Ra was observed from the soft tissues within the first 24 h, the bone uptake of 223Ra, which was not significantly different from maximum after only 1 h, was not significantly reduced during the 14 d. Furthermore, little redistribution of 223Ra daughter products away from bone was found (2% at 6 h and less than 1% at 3 d). Estimates of dose to marrow cavities showed that the 223Ra α-emitter might have a marrow-sparing advantage compared with β-emitters for targeting osteoid surfaces because the short-range α-particles irradiate a significantly lower fraction of the marrow volumes. At the same time, the bone surfaces will receive a therapeutically effective radiation dose. Conclusion: The results of this study indicate that 223Ra is a promising candidate for high-linear-energy transfer α-particle irradiation of cancer cells on bone surfaces. 223Ra can, together with its daughter radionuclides, deliver an intense and highly localized radiation dose to the bone surfaces with substantially less irradiation of healthy bone marrow compared with standard bone-seeking β-emitters.