Combination of everolimus with trastuzumab plus paclitaxel as first-line treatment for patients with HER2-positive advanced breast cancer (BOLERO-1) : a phase 3, randomised, double-blind, multicentre trial

Abstract

BACKGROUND : mTOR inhibition has been shown to reverse trastuzumab resistance from hyperactivated the PIK/AKT/mTOR pathway due to PTEN loss, by sensitizing PTEN-deficient tumors towards trastuzumab. The BOLERO-1 study evaluated the efficacy and safety of adding everolimus to trastuzumab and paclitaxel as first-line therapy for HER2+ advanced breast cancer (ABC). METHODS : In this phase III, randomized, double-blind trial, patients were enrolled across 141 sites in 28 countries. Eligible patients were ≥18 years of age, with locally assessed HER2+ advanced breast cancer (ABC), with Eastern Cooperative Oncology Group performance status of 0-1, who had not received prior trastuzumab or chemotherapy for ABC, had measurable disease as per Response Evaluation Criteria in Solid Tumors or bone lesions in the absence of measurable disease, without prior systemic therapy for advanced disease except endocrine therapy. The patients were randomized 2:1 (with an interactive voice and web response system) to receive either daily everolimus (10 mg/day) orally or placebo plus weekly trastuzumab intravenously at 4 mg/kg loading dose on Day-1 with subsequent weekly doses of 2 mg/kg of each 4-week cycle plus paclitaxel intravenously at a dose of 80 mg/m2 on days 1, 8, and 15 of each 4- week cycle. Randomization was stratified according to prior use of trastuzumab and visceral metastasis. Patients and investigators were blinded to the assigned treatments. Identity of experimental treatments was concealed by use of everolimus and placebo that were identical in packaging, labelling, appearance, and administration schedule. The two primary objectives were investigator-assessed progression-free survival (PFS) in the full study population and in the subset of patients with hormone receptor-negative (HR) breast cancer at baseline; the latter was added during the course of the study, prior to unblinding based on new clinical and biological findings from other studies. All efficacy analyses were based on the intention-to-treat population. Enrolment for this trial is closed and results of the final PFS analyses are presented here. Clinicaltrials.gov identifier: NCT00876395. FINDINGS : Between 10-Sep-2009 and 16-Dec-2012, 719 patients were randomized to receive everolimus (n=480) or placebo (n=239). Median follow-up was 41.3 months (IQR: 35.4 – 46.6 months). INTERPRETATION : The primary objective in the full population was not met; median PFS was 15.0 months with everolimus vs 14.5 months with placebo (hazard ratio, 0.89; 95% CI, 0.73-1.08; p=0.1166). In the HR subpopulation (n=311), median PFS with everolimus was 20.3 months vs 13.1 months with placebo (hazard ratio, 0.66; 95% CI, 0.48-0.91; p=0.0049), however, the protocol-specified statistical significance threshold (p=0.0044) was not crossed. The most common adverse events (AEs) with everolimus vs placebo were stomatitis (314 [66.5%] vs 77 [32.4%] patients), diarrhea (267 [56.6%] vs 111 [46.6%] patients), and alopecia (221 [46.8%] vs 125 [52.5%]). The most frequently reported grade 3/4 AEs in the EVE arm vs PBO arm were neutropenia (117 [24.8%] of 472 patients vs 35 [14.7%] of 238 patients), stomatitis (59 [12.5%] of 472 patients vs 3 [1.3%] of 238 patients), anemia (46 [9.7%] of 472 patients vs 6 [2.5%] of 238 patients) and diarrhea (43 [9.1%] of 472 patients vs 10 [4.2%] of 238 patients) On-treatment AE-related deaths were reported in 17 [3.6%] vs 0% of patients respectively.Interpretation: The primary objective of PFS was not met. However, consistent with the preliminary observations from BOLERO-3, everolimus prolonged median PFS by 7.2 months in patients with HR, HER2+ ABC, which warrants further investigation. The safety profile was generally consistent with what was previously reported in BOLERO-3. Proactive monitoring and early management of AEs in patients treated with everolimus and chemotherapy is critical..