The addition of DTPA to [177Lu-DOTA0,Tyr3]octreotate prior to administration reduces rat skeleton uptake of radioactivity
- 1 February 2003
- journal article
- research article
- Published by Springer Nature in European Journal of Nuclear Medicine and Molecular Imaging
- Vol. 30 (2) , 312-315
- https://doi.org/10.1007/s00259-002-1054-4
Abstract
Peptide receptor-targeted radionuclide therapy is nowadays also being performed with DOTA-conjugated peptides, such as [DOTA0,Tyr3]octreotate, labelled with radionuclides like 177Lu. The incorporation of 177Lu is typically ≥99.5%; however, since a total patient dose can be as high as 800 mCi, the amount of free 177Lu3+ (= non-DOTA-incorporated) can be substantial. Free 177Lu3+ accumulates in bone with unwanted irradiation of bone marrow as a consequence. 177Lu-DTPA is reported to be stable in serum in vitro, and in vivo it has rapid renal excretion. Transforming free Lu3+ to Lu-DTPA might reroute this fraction from accumulation in bone to renal clearance. We therefore investigated: (a) the biodistribution in rats of 177LuCl3, [177Lu-DOTA0,Tyr3]octreotate and 177Lu-DTPA; (b) the possibilities of complexing the free 177Lu3+ in [177Lu-DOTA0,Tyr3]octreotate to 177Lu-DTPA prior to intravenous injection; and (c) the effects of free 177Lu3+ in [177Lu-DOTA0,Tyr3]octreotate, in the presence and absence of DTPA, on the biodistribution in rats. 177LuCl3 had high skeletal uptake (i.e. 5% ID per gram femur, with localization mainly in the epiphyseal plates) and a 24-h total body retention of 80% injected dose (ID). [177Lu-DOTA0,Tyr3]octreotate had high and specific uptake in somatostatin receptor-positive tissues, and 24-h total body retention of 19% ID. 177Lu-DTPA had rapid renal clearance, and 24-h total body retention of 4% ID. Free 177Lu3+ in [177Lu-DOTA0,Tyr3]octreotate could be complexed to 177Lu-DTPA. Accumulation of 177Lu in femur, blood, liver and spleen showed a dose relation to the amount of free 177Lu3+, while these accumulations could be normalized by the addition of DTPA. After labelling [DOTA0,Tyr3]octreotate with 177Lu the addition of DTPA prior to intravenous administration of [177Lu-DOTA0,Tyr3]octreotate is strongly recommended.Keywords
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