ERBB2 and breast cancer: According to the 4th European Society of Oncology - European Society for Medical Oncology (ESO-ESMO) International Consensus Guidelines for Advanced Breast Cancer, breast cancer treatment should be guided by HR and HER2 status, previous therapies and the associated toxicity, stage of the disease (locally advanced or metastatic), age, menopausal status (important in terms of endocrine therapy) and comorbidities.