For example, randomized controlled trials are conducted in metastatic HER2-positive BC patients who had high risk factors to develop BM to explore whether the regular head MRI screening would be good for the early diagnosis and treatment, or there could be clinical trials to explore whether small-molecule tyrosine kinase inhibitors used in adjuvant therapy or first-line advanced salvage treatment would decrease the occurrence of BM, and ultimately improve the prognosis of brain metastasis in HER2-positive BC patients. Here, ERBB2 is linked to breast cancer.