HORMONE THERAPY IN ADVANCED ER+/HER2- NEGATIVE BREAST CANCER WITH PI3K INHIBITORS: A REVIEW OF THE LITERATURE

Breast cancer is a heterogenous disease, showing as several different clinical and histologic types. Most of breast cancers express hormone receptors for estrogen and progesterone, which are considered as estrogen receptor-positive and progesterone-receptor-positive, respectively. Endocrine therapy was the first class of target-directed therapy approved for treating breast cancer and is still very important for the treatment of HR+ breast cancer because of its effectiveness and good toxicity profile. It targets receptor-mediated signaling pathways implicated in cell survival and proliferation, such as those mediated by hormone receptors. Although these approaches have improved the management of advanced breast cancer, many patients either fail to respond to initial therapy (primary or de novo resistance) or eventually become resistant to treatment (secondary or acquired resistance). To expand the use of existing endocrine treatments and their efficiency, new methods are needed. Such new approaches would boost the benefit of existing endocrine therapy by extending time to disease progression, avoiding or overcoming resistance to endocrine treatment, and delaying the use of chemotherapy. This article will review the central role of the PI3K inhibitors in driving ER+/HER2- breast tumors. Also, schemes to combine pathway inhibitors with endocrine therapy for better patient outcome, and approaches to identify patient populations that would benefit most from inhibition of the PI3K/AKT/mTOR pathway will be assessed.