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 letrozole, anastrozole, or exemestane, to be selected by the investigator. The primary objective of ALTERNATIVE is to examine the efficacy of L/T/AI compared with T/AI alone. The primary efficacy endpoint is overall survival (OS; time from randomization until death due to any cause) for L/T/AI vs T/AI. Secondary efficacy objectives include: comparisons of OS between T/AI and L/AI as well as between T/L/AI and L/AI, comparisons of progression-free survival, overall response rate, time to response, duration of response, safety, and tolerability for all 3 treatment groups. The study is powered to detect a 42% reduction in risk of death (hazard ratio=0.70) in patients who receive L/T/AI (median 28.5 months) vs T/AI (median 20 months) using a 1-sided test for superiority with α=0.025. The required number of total events to achieve a power of 80% is 249. Secondary comparisons are not powered and will be based on the ITT population. This study is currently recruiting, with a target of 525 patients. If its objectives are reached, it will provide a valuable, chemotherapy-free treatment option for HER2+/HR+ MBC patients. Clinical trial registry number: NCT01160211.