Safety and Efficacy of Everolimus With Exemestane vs Exemestane Alone in Elderly Patients With HER2-Negative, Hormone Receptor-Positive Breast Cancer in BOLERO-2

SUMMARY: Exemestane (AROMASIN®) is a steroidal, Aromatase Inhibitor (AI) which has been shown to improve Progression Free Survival (PFS) in postmenopausal patients with ER positive metastatic breast cancer. Patients tend to have limited clinical benefit with subsequent hormonal interventions if their disease recurs or progresses on AI’s. Further, cytotoxic chemotherapy may not be feasible in elderly patients. The PI3K/AKT/mTOR is a complex pathway, essential for cell proliferation, survival and apoptosis (programmed cell death). This pathway is of interest because of its increased activity in malignant cells as a result of amplification or mutation of the genes associated with PI3-kinase (phosphatidylinositol-3 kinase) and AKT, as well as loss of function of PTEN. PTEN normally prevents activation of AKT and its downstream pathways. Elevated ER signaling and breast cancer progression has been associated with activation of this mTOR (mammalian Target Of Rapamycin) pathway. Everolimus (AFINITOR®) is a mTOR inhibitor that has been shown to inhibit ER signaling and restore sensitivity to anti-estrogen therapies. In the phase III BOLERO-2 study, patients with ER positive, advanced breast cancer, who had recurred or progressed on prior therapy with nonsteroidal AI’s such as Anastrozole (ARIMIDEX®) or Letrazole (FEMARA®), had doubling of PFS with a combination of AROMASIN® and AFINITOR® compared to AROMASIN® alone. The authors now report the Safety and Efficacy of AROMASIN® and AFINITOR® combination in 316 patients, 65 years of age or older, out of the 724 patients in the BOLERO-2 study. The median follow up was 18 months. Baseline treatment characteristics were similar in all treatment subsets. The treatment combination resulted in 55% reduction in the risk of disease progression regardless of the age compared to AROMASIN® alone (PFS – 7.8 months vs 3.2 months, HR=0.45, P<0.0001). Further the combination treatment resulted in greater clinical benefit compared to single agent AROMASIN®. Approximately two third of the patients regardless of their age required dose modifications and the most common adverse events in all age groups with similar incidences were stomatitis, rash, fatigue , hyperglycemia and pneumonitis. It is recommended that elderly patients be carefully monitored and toxicities promptly addressed during treatment. The authors concluded that a combination of AROMASIN® and AFINITOR® can provide significant clinical benefit with acceptable toxicities, even in patients 65 years of age or older, thereby delaying the need for chemotherapy. Pritchard KI, Burris HA, Ito Y, et al. Clinical Breast Cancer 2013;13:421-432.