A phase II study of lapatinib for brain metastases in patients with HER2-overexpressing breast cancer following trastuzumab based systemic therapy and cranial radiotherapy: subset analysis of Japanese patients

Background It is known that one third of patients with human epidermal growth factor receptor 2 (HER2)-overexpressing metastatic breast cancer (MBC) treated with trastuzumab will develop brain metastases. As the development of brain metastases is fatal, controlling its progression is clinically meaningful. However, effective therapy for MBC patients with brain metastasis after cranial radiation is limited. The international clinical study in which six Japanese patients participated indicated the antitumor activity of lapatinib against brain metastases of HER2-overexpressing breast cancer.