In vitro evaluation of no carrier added, carrier added and cross-complexed [90Y]-EDTMP provides evidence for a novel 'foreign carrier theory'

The present study focused on the preparation of novel bone tracers containing yttrium as radionuclide or carrier. Moreover, these preparations were comparatively evaluated in vitro on the basis of a recently presented pre vivo model comprising binding studies on synthetic and human bone powder. It was shown that among the therapeutic radionuclides, no carrier added [ 90 Y]-EDTMP exceeded [ 188 Re]-EDTMP while yielding lower binding values than [ 153 Sm]-EDTMP. Furthermore, the authors investigated the influence of “foreign” carriers added to [ 90 Y]-EDTMP, [ 99m Tc]-EDTMP and [ 111 In]-EDTMP by the method of cross-complexation. The findings reveal a new paradigm: a carrier more foreign to the complexed radionuclide causes a higher binding increase on human bone matrices in vitro than a more “related” carrier.