ALTERNATIVE (EGF114299): A study of lapatinib, trastuzumab, and endocrine therapy in patients who received neo-/adjuvant trastuzumab (IV) and endocrine therapy.

TPS661 Background: Approximately 50% of human epidermal growth factor receptor 2 positive (HER2+) breast cancers are also hormone receptor-positive (HR+). For patients with HER2+/HR+ disease, combining the aromatase inhibitor (AI) letrozole with the dual tyrosine kinase inhibitor lapatinib (L) has been shown to improve outcomes vs letrozole alone. Similar results were found for the combination of trastuzumab (T; a humanized monoclonal antibody targeting HER2) and anastrozole vs anastrozole alone. Finally, the combination of L and T has been shown to improve outcomes vs L alone. Methods: This phase III, randomized, open-label, multicenter trial (ALTERNATIVE) will enroll postmenopausal female patients with HER2+/HR+ metastatic breast cancer (MBC) who have not received prior treatment for MBC, have received neo/adjuvant T and endocrine therapy, and are not candidates for chemotherapy. Patients will be randomized 1:1:1 to 1 of 3 treatment arms: L plus T plus an AI; T plus an AI; or L plus an AI. The AI can be...