In multiple breast cancer clinical trials (Asghar et al, 2015; DeMichele et al, 2015; Finn et al, 2015, 2016; Cristofanilli et al, 2016; Hamilton & Infante, 2016; Sherr et al, 2016), PD0332991 combined with endocrine treatment substantially improved progression‐free survival compared to endocrine treatment alone in women with ER‐positive/HER2‐negative advanced breast cancer. Here, ERBB2 is linked to breast cancer.