A clinical study including 719 patients with HR+ breast cancer demonstrated that the clinical benefit rate (CBR) of endocrine therapy was significantly lower in the high serum HER2 group than in the low HER2 group (23% vs 45%, p < 0.0001), with a significant reduction in time to disease progression (TTP) and overall survival (OS) (p < 0.0001) (10). Here, ERBB2 is linked to breast carcinoma.