BOLERO-2 Halted After Positive Interim Analysis

An interim analysis of a phase III study of Afinitor (everolimus) tablets combined with exemestane in women with breast cancer revealed that the regimen significantly extended progression-free survival (PFS) compared to placebo plus exemestane, which put an early end to the trial.

Known as BOLERO-2 (Breast cancer trials of OraL EveROlimus-2), this trial was a randomized, double-blind study involving more than 700 postmenopausal women from 195 sites worldwide. Each participant in the study had estrogen receptor—positive (ER+), human epidermal growth factor receptor 2 (HER2)­–negative metastatic breast cancer, whose disease had already progressed despite endocrine therapy with nonsteroidal aromatase inhibitors. Patients who had received more than 1 regimen of chemotherapy for advanced breast cancer were not included in the study. Progression-free survival was the primary endpoint of this trial.

While enrolled in the study, patients were divided into 2 groups. One group received continuous therapy with oral everolimus 10 mg/day, while the second arm received placebo plus oral exemestane 25 mg/day. Twice as many patients were randomized to the everolimus group than the placebo group.

Everolimus works by targeting the mTOR protein in cancer cells that helps regulate tumor cell division and cell metabolism. The study sponsor, Novartis, did not specify in its statement the PFS rates in the 2 sets of patients, or provide data on the secondary endpoints of overall survival, overall response rate, incidence of adverse events, patient-reported outcomes, or the clinical benefit rate. Aside from this, Novartis did note that results from the study would be presented at a medical conference this year.