Recent advances in the treatment of hormone receptor positive HER2 negative metastatic breast cancer.

Endocrine therapy is the recommended systemic therapy for hormone receptor (HR) positive metastatic breast cancer (MBC). However so far the limited number of endocrine agents and the onset of endocrine resistance have severely limited the therapeutic options for this patients. In the last years many targeted agents have been investigated to prevent or overcome endocrine resistance; only a few of them have been found effective in HR positive MBC, such as everolimus, CK4/6 inhibitors and HDAC inhibitors. Furthermore, translational medicine studies using next generation sequencing technologies have evaluated genetic variations of a broad panel of cancer-related genes and explored their correlations with targeted agents benefit. In some studies predictive biomarkers have been identified and many ongoing studies are evaluating the efficacy of targeted drugs in HR positive MBC patients selected for biomarkers or stratified by pathways amplification.