ERBB2 and breast cancer: In the PERMEATE phase II study, pyrotinib plus capecitabine achieved a 74.6% intracranial objective response and yielded a median intracranial PFS of roughly 11 months in individuals with HER2 positive BC and existing brain metastases who had not yet received cranial radiotherapy, underscoring the capacity of small-molecule HER2 inhibitors to improve CNS disease control (24).