In the MDA-MB-231/H2N xenograft model, which is characterized by low expression of HER2 and moderate expression of EGFR, the bispecific 64Cu-NOTA-Fab-PEG24-EGF showed much greater tumor uptake (4.9% ID/g at 48 h p. i.)than those of the radiolabeled Fab (against HER2) and EGF monomers (1.9% ID/g and 0.7% ID/g, respectively). The gene discussed is ERBB2; the disease is neoplasm.