The potential for using nanoparticles to deliver Auger electron radiotherapy has been demonstrated in studies conducted by the Reilly and Allen groups.16–20 For example, block copolymer micelles of ∼30 nm diameter surface-labelled with trastuzumab (Tz) were used to target 111In to Her2-positive breast cancer cells.20 Although DNA damage was not investigated, these investigators showed that radiotoxicity could be enhanced by increasing nuclear targeting of 111In by addition of a nuclear localisation signal to Tz (with ∼8% of total internalised radioactivity accumulating in cell nuclei). Here, ERBB2 is linked to breast cancer.