ERBB2 and neoplasm: Two factors might be contributing to the difference of the observation on therapeutic effects between targeted vs non-targeted: (1) the injected dose (3 MBq) in the HER2 targeted study was 50% lower than in the EGFR targeted study (4.5 MBq); (2) the tumour model (MDA-MB-361 xenografts in NOD/SCID mice, tumour doubling time of 5 d for untreated control) used in the HER2 targeted study was 3.5 times more aggressive than MDA-MB-468 xenografts in CD-1 athymic mice (tumour doubling time of 17 d for untreated control) used in the EGFR targeted study.