RT Journal Article
SR Electronic
T1 Combination Radionuclide Therapy Using <sup>177</sup>Lu- and <sup>90</sup>Y-Labeled Somatostatin Analogs
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 13S
OP 17S
VO 46
IS 1 suppl
A1 Marion de Jong
A1 Wout A.P. Breeman
A1 Roelf Valkema
A1 Bert F. Bernard
A1 Eric P. Krenning
YR 2005
UL http://jnm.snmjournals.org/content/46/1_suppl/13S.abstract
AB Peptide receptor-targeted radionuclide therapy of somatostatin receptor-expressing tumors is a promising application of radiolabeled somatostatin analogs. Suitable radionuclides are 90Y, a pure, high-energy β-emitter (2.27 MeV), and 177Lu, a medium-energy β-emitter (0.5 MeV) with a low-abundance γ. Methods: Lewis rats, each bearing both a small (approximately 0.5 cm2) and a large (7–9 cm2) somatostatin receptor-positive rat pancreatic CA20948 tumor in their flanks, were used. We investigated the radiotherapeutic effects of [90Y-tetraazacyclododecanetetraacetic acid (DOTA),Tyr3]octreotide, [90Y-DOTA,Tyr3]octreotate, [177Lu-DOTA,Tyr3]octreotate, and the combination of 90Y- and 177Lu-labeled analogs at the same tumor radiation dose (60 Gy). Results: Radiotherapeutic effects of the 90Y- and 177Lu-labeled analogs were found in the rat tumor model. In these animals bearing tumors of different sizes, the antitumor effects of the combination of 50% 177Lu- plus 50% 90Y-analogs were superior to those in animals treated with either 90Y- or 177Lu- analog alone. In smaller tumors, the 90Y radiation energy was not completely absorbed in the tumor, whereas in larger tumors the increased number of clonogenic tumor cells at the fixed level of absorbed dose may account for the failure of 177Lu alone to go completely into remission. Conclusion: This study shows the superior antitumor effects of the combination of 177Lu- and 90Y-somatostatin analogs when compared with either 90Y- or 177Lu-analog alone in animals bearing tumors of various sizes.