Specifically, the TBCRC049 study, an investigator-initiated phase 2 single-arm study clinical trial enrolling to evaluate the safety and efficacy of tucatinib, trastuzumab, and capecitabine in HER2+ BC with newly diagnosed lymph node metastasis, demonstrated that tucatinib distributed into the cerebrospinal fluid [81]. This evidence concerns the gene ERBB2 and breast cancer.