ERBB2 and metastatic malignant neoplasm: The third one is “Trastuzumab duocarmazine in locally advanced and metastatic solid tumours and HER2-expressing breast cancer: a phase 1 dose-escalation and dose-expansion study”revealing that Trastuzumab duocarmazine demonstrates significant clinical efficacy in extensively treated patients with HER2-expressing metastatic cancers, including those resistant to HER2-positive trastuzumab emtansine and with HER2-low breast cancer, while maintaining a manageable safety profile.