LAUSR

Key Points Question Can tucatinib, trastuzumab, and capecitabine provide systemic and intracranial benefit for patients with ERBB2 (HER2)-positive metastatic breast cancer and brain metastases? Findings In this exploratory subgroup analysis of a randomized clinical trial of 612 patients with ERBB2-positive breast cancer, overall survival, intracranial efficacy, and new brain lesion–free survival were evaluated. Tucatinib in combination with trastuzumab and capecitabine prolonged median overall survival by 9.1 months in patients with brain metastases and reduced the risk of developing new brain lesions as sites of first progression or death by 45.1% in all patients. Meaning Findings suggest tucatinib in combination with trastuzumab and capecitabine provides survival benefits and delays development of new brain lesions, representing an important treatment option for patients with ERBB2-positive metastatic breast cancer, including those with brain metastases.