First-Line Chemotherapy for Metastatic Breast Cancer

The selection of first-line chemotherapy for metastatic breast cancer (MBC) is complex because of the myriad of treatment options available and the inherent biologic heterogeneity of the disease. The potential treatment options are greatly influenced by estrogen and progesterone receptor and HER2 status of the tumor, and biopsy with reassessment of these markers at the time of disease recurrence is strongly recommended. Metastatic breast cancer is generally an incurable disease, with survival that could range from months to several years. Important but modest improvements in overall survival (OS) have been observed for women with MBC over the past few decades, in part because of improvements in systemic therapy. For women with endocrine-responsive disease, hormonal therapy is the appropriate initial treatment choice at the time of disease recurrence with rare exception. Initiation of systemic chemotherapy is appropriate for women with disease that is either hormone receptor negative, endocrine therapy refractory, or rapidly progressive with visceral involvement. The addition of trastuzumab to chemotherapy for women with HER2-positive breast cancer represents a clear standard of care. For HER2-negative MBC, sequential single-agent chemotherapy is preferred over combination therapy as a result of the more favorable toxicity profile and absence of a clinically significant improvement in survival with combination treatment. Many single-agent chemotherapeutic agents have activity in MBC, with most data supporting an anthracycline- or taxone-based approach. Bevacizumab in combination with chemotherapy prolongs progression-free survival in women with MBC, though its position in the first-line treatment of MBC relative to standard chemotherapy remains unclear at this time because of lack of OS benefit.