In addition, both [99mTc]Tc-ADAPT6 and [99mTc]Tc-(HE)3-G3 have significantly (p < 0.05, Mann–Whitney test) higher tumour-to-contralateral site ratios for clinically HER2-positive primary breast tumours compared to HER2-negative, which indicates that they could be used for the stratification of patients for HER2-targeting therapies. This evidence concerns the gene ERBB2 and breast neoplasm.