The BOLERO-2 Trial: The Addition of Everolimus to Exemestane in the Treatment of Postmenopausal Hormone Receptor-Positive Advanced Breast Cancer

The combination of the mTOR inhibitor everolimus with the aromatase inhibitor exemestane was evaluated in the randomized Phase III BOLERO-2 trial. Research has indicated that aberrant signaling through the mTOR pathway is associated with resistance to endocrine therapies. The BOLERO-2 trial examined the effects on progression-free survival of the addition of everolimus to exemestane in a patient population of postmenopausal, hormone receptor-positive, advanced breast cancer. At the interim analysis, the median progression-free survival assessed by local investigators was 6.9 months for everolimus plus exemestane versus 2.8 months for placebo plus exemestane (hazard ratio: 0.43; p < 0.001), and by central assessment was 10.6 versus 4.1 months, respectively (hazard ratio: 0.36; p < 0.001). The everolimus plus exemestane arm showed greater number of grade 3 and 4 adverse events. This study suggests that the addition of everolimus to exemestane is a potential viable treatment option for this patient population.