The somatostatin analogue [DOTA0,Tyr3]octreotate has nine-fold higher affinity for the somatostatin receptor subtype 2 as compared with [DOTA0, Tyr3]octreotide. Also, labelled with the beta- and gamma-emitting radionuclide lutetium-177, this compound has been shown to have a very favourable impact on tumour regression and animal survival in a rat model. Because of these reported advantages over the analogues currently used for somatostatin receptor-mediated radiotherapy, we decided to compare [177Lu-DOTA0,Tyr3]octreotate (177Lu-octreotate) with [111In-DTPA0]octreotide (111In-octreotide) in six patients with somatostatin receptor-positive tumours. Plasma radioactivity after 177Lu-octreotate expressed as a percentage of the injected dose was comparable with that after 111In-octreotide. Urinary excretion of radioactivity was significantly lower than after 111In-octreotide, averaging 64% after 24 h. The uptake after 24 h, expressed as a percentage of the injected dose of 177Lu-octreotate, was comparable to that after 111In-octreotide for kidneys, spleen and liver, but was three- to fourfold higher for four of five tumours. The spleen and kidneys received the highest absorbed doses. The doses to the kidneys were reduced by a mean of 47% after co-infusion of amino acids. It is concluded that in comparison with the radionuclide-coupled somatostatin analogues that are currently available for somatostatin receptor-mediated radiotherapy, 177Lu-octreotate potentially represents an important improvement. Higher absorbed doses can be achieved to most tumours, with about equal doses to potentially dose-limiting organs; furthermore, the lower tissue penetration range of 177Lu as compared with 90Y may be especially important for small tumours.

Octreotate, Peptide receptor radiotherapy, Somatostatin, Somatostatin receptor imaging
dx.doi.org/10.1007/s002590100574, hdl.handle.net/1765/63516
European Journal of Nuclear Medicine
Department of Nuclear Medicine

Kwekkeboom, D.J, Bakker, W.H, Kooij, P.P.M, Konijnenberg, M, Srinivasan, A, Erion, J.L, … Krenning, E.P. (2001). [177Lu-DOTA0,Tyr3]octreotate: Comparison with [111In-DTPA0]octreotide in patients. European Journal of Nuclear Medicine, 28(9), 1319–1325. doi:10.1007/s002590100574