EGFR and breast cancer: Previous in vitro studies from the same group demonstrated that targeted nanohybrids exhibited high EGFR‐binding and internalization into human breast cancer cells, and were strongly cytotoxic to cells with high EGFR expression, but were less effective with breast cancer cells with low EGFR density.[29] However, in vivo EGFR targeting did not provide greater tumor retention or better tumor radiation‐absorbed doses, as the two hybrids (i.e., 177Lu‐AuNP‐panitumumab and 177Lu‐AuNP) were equally effective for local treatment of breast cancer xenografts in mice.