Clinical trials update: Medical management of advanced breast cancer

Selection of treatment for metastatic breast cancer depends on several factors: the status of estrogen receptors or progesterone receptors on breast cancer cells and the expression levels of human epidermal growth factor receptor-2. The presence of estrogen or progesterone receptors typically indicates slower-growing tumors that may be amenable to hormonal manipulation, which provides significant disease control while offering a better toxicity profile than conventional chemotherapy. The understanding of hormonal therapies in patients with postmenopausal metastatic breast cancer has advanced greatly in the past several decades. Aromatase inhibitors, although used initially as second-line therapy, recently have proved to be as effective as tamoxifen, if not superior to it, as first-line therapy for metastatic breast cancer. New data also suggest that letrozole provides significantly better objective responses than anastrozole as second-line therapy. Exemestane, a steroidal aromatase inhibitor, is an effective third-line therapy. Fulvestrant, an estrogen receptor antagonist with no known agonist effect, provides a new option for hormonal therapy. For patients with metastatic breast cancer and overexpression of human epidermal growth factor receptor-2 on tumor cells, the monoclonal antibody trastuzumab is the preferred option, either in combination with paclitaxel as first-line treatment, or as a single agent for second-line therapy. By extending the sequence of hormonal therapy, disease progression and the need for chemotherapy may be significantly delayed, potentially extending patient survival rates and improving quality of life.