The biodistribution of [111In]In-DOTA-trastuzumab (7–8 MBq; 20 μg) mixed with DOTA-trastuzumab (18 μg) and coinjected with 4 kBq (1.5 μg) of [225Ac]Ac-DOTA-trastuzumab (total mass = 40 μg) or equivalent amounts of irrelevant [111In]In-DOTA-IgG1 coinjected with [225Ac]Ac-DOTA-IgG1 (total mass = 40 μg) at 48 h p.i. in NRG mice with s.c. HER2-positive 164/8-1B/H2N.luc+ human BC tumours are shown in Fig. 5a. Here, ERBB2 is linked to neoplasm.