ERBB2 and breast cancer: Next to chemotherapy, considerable effort has been invested to develop targeted therapies which inhibit specific molecular drivers of cancer progression, providing distinct subsets of patients carrying these mutations with a significant benefit of survival.38 This has particularly important implications for the treatment of brain metastasis, since patients carrying some of these mutations have a higher propensity to develop brain metastasis (such as EGFR-mutant NSCLC or HER2+ breast cancer).