BOLERO-1: A randomized, phase III, double-blind, placebo-controlled multicenter trial of everolimus in combination with trastuzumab and paclitaxel as first-line therapy in women with HER2-positive (HER2+), locally advanced or metastatic breast cancer (BC).

Abstract

TPS648 Background: Up to 25% of BCs overexpress human epidermal growth factor receptor 2 (HER2). Patients with HER2+ disease have a higher rate of relapse and shorter overall survival (OS). Trastuzumab, a monoclonal antibody targeting HER2, is the standard of care and improves OS for HER2+ BC, but acquired resistance is common. The combination of trastuzumab and paclitaxel has shown good tolerability and excellent objective response rates (ORR) in up to 84% of patients with HER2+ metastatic BC (MBC) (Gasparini G, et al. BCRT. 2007;101:355-65). Everolimus is an orally bioavailable inhibitor of mammalian target of rapamycin (mTOR), a protein kinase central to multiple protein synthesis pathways and implicated in trastuzumab resistance. Everolimus-containing regimens have shown promising results in patients with ER+, HER2– advanced BC in phase II/III trials; everolimus plus trastuzumab/paclitaxel or vinorelbine has shown encouraging ORR with an acceptable safety profile in phase I/II trials in patients with HER2+ MBC. The present phase III study was undertaken to assess the effectiveness of adding everolimus to first-line standard therapy in HER2+ advanced BC. Methods: Women with HER2+, locally advanced or metastatic BC who have received no prior systemic therapy (except endocrine) are eligible. Local disease must not be amenable to resection with curative intent. Women with a history of central nervous system metastasis are excluded. Patients are randomized 2:1 (everolimus vs control) to receive standard therapy (paclitaxel and trastuzumab) plus everolimus (10 mg daily) or placebo. The primary endpoint is progression-free survival. Secondary endpoints include OS, ORR, and clinical benefit rate. Additional endpoints are safety, performance status, and biomarkers. This trial is sponsored by Novartis Pharmaceuticals and is registered (ClinicalTrials.gov: NCT00876395). Enrollment began September 2009, with a planned accrual of 717. The current accrual is 719, and the estimated primary completion date is October 2012.