In this study we investigated the influence of co-injection of the non-labeled trivalent anti-HER3 affibody molecule on biodistribution and tumor targeting of radiocobalt-labeled monomer ([57Co]Co-NOTA-Z08699, where NOTA is 1,4,7-triazacyclononane-N,N′,N′′-triacetic acid). This evidence concerns the gene ERBB3 and neoplasm.