It has been approved in combination with an AI for the treatment of HR-positive, HER2-negative advanced BC as a first line ET in postmenopausal women or in combination with fulvestrant for the treatment of HR-positive, HER2-negative advanced or metastatic BC in women with disease progression following endocrine therapy, on the basis of the PALOMA 2 study [62] and PALOMA 3 study [63], respectively. This evidence concerns the gene ERBB2 and breast cancer.