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,
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