Everolimus in Postmenopausal, Hormone Receptor-Positive Advanced Breast Cancer: Summary and Results of an Austrian Expert Panel Discussion

In patients with hormone receptor-positive advanced breast cancer, response to endocrine therapy is frequently limited by endocrine resistance. One important mechanism of resistance is related to mammalian target of rapamycin (mTOR), a molecule involved in the activation of alternative signaling pathways. Preclinically, resensitization of endocrine resistance can be achieved by the addition of the mTOR inhibitor everolimus to endocrine therapy. Recent results of clinical trials confirmed the clinical activity of combining everolimus and endocrine therapy in neoadjuvant and advanced breast cancer. The BOLERO-2 trial demonstrated significant progression-free survival benefits for the addition of everolimus to exemestane. These data were the basis for the recent approval of everolimus in combination with exemestane for the treatment of advanced hormone receptor-positive breast cancer. In clinical practice, the following 3 patient groups are particularly suitable for this treatment: those with progression on aromatase inhibitor therapy, those who respond well to chemotherapy and might benefit from subsequent endocrine therapy, and those with non-aggressive tumor biology. Everolimus treatment requires careful clinical monitoring due to the potentially serious side effects, e.g. stomatitis and pneumonitis. It is also important to educate patients and physicians in order to increase their awareness of side effects. At present, everolimus is investigated in clinical trials.