Therapy for HER2-Positive Metastatic Breast Cancer

To the Editor: Murthy et al. (Feb. 13 issue) 1 have shown that tucatinib prolongs survival among patients who have previously received treatment for human epidermal growth factor receptor 2 (HER2)–positive breast cancer. Its activity in patients with brain metastases is encouraging. The combination of tucatinib and capecitabine as agents with central nervous system (CNS) activity, paired with trastuzumab for extracranial control, is appealing, especially given its acceptable safety profile. To fully evaluate tucatinib, measures in addition to overall survival are essential. The mainstay of treatment for cerebral metastases is still radiotherapy. 2 Given that the majority of patients had already been . . .