ERBB2 and neoplasm: Yet, the impact of previous treatment with trastuzumab on the risk of CNS metastases occurrence is debated, as these results were not reproduced in other studies.12,34,45 Of note, the fact that most patients with CNS metastases have a HER2−/HR+ tumour (45.3%) despite an increased risk of CNS metastases in patients with a HER2-positive and/or a HR-negative tumour is linked with the fact that the incidence of HER2−/HR+ tumours is higher.