Borges VF, et al. - In the treatment of patients with ERBB2/HER2-positive metastatic breast cancer (MBC) with and without brain metastases, researchers determined the maximum tolerated dosage of tucatinib in combination with ado-trastuzumab emtansine (T-DM1) by analyzing the data of 57 study participants recruited between January 22, 2014, and June 22, 2015. Participants were 18 years of age or older with ERBB2/HER2-positive MBC previously treated with trastuzumab and a taxane. Among heavily pretreated patients with ERBB2/HER2-positive MBC with and without brain metastases, tucatinib plus T-DM1 seemed to have acceptable toxicity and to show preliminary antitumor activity.