ERBB2 and breast cancer: In the current national and international guidelines for the treatment of HER2-positive breast cancer with brain metastases, the TKI tucatinib and the ADC trastuzumab-deruxtecan are currently recommended as first line therapy for systemic therapy regimes (Le Rhun et al., 2021; Vogelbaum et al., 2022; Müller et al., 2025).