Comparable results were obtained by Howe et al.14 for treatment of s.c. HER2-positive BT-474 tumorsin athymic mice administered a single higher amount (9.2 kBq) of[225Ac]Ac-DOTA-trastuzumab IgG, in which tumor growth wasinhibited but not arrested, despite the tumor dose (6.7 Gy) being2.3-fold higher than in our study. Here, ERBB2 is linked to neoplasm.