Targeted therapy has dramatically improved the OS of patients with BrM (Valiente et al., 2018), for instance, osimertinib targeting epidermal growth factor receptor (EGFR) mutated non-small cell lung cancer (NSCLC) BrM, lapatinib targeting human epidermal growth factor receptor 2 (HER-2) mutated breast cancer, and B-Raf kinase gene (BRAF) inhibitor dabrafenib combined with the mitogen-activated protein kinase (MAPK) pathway inhibitor trametinib targeting melanoma (Achrol et al., 2019). The gene discussed is ERBB2; the disease is breast cancer.