Metastatic breast cancer: the treatment challenge.

As therapeutic options have multiplied, chemotherapy for metastatic breast cancer (MBC) has become increasingly complex. Furthermore, advances in the treatment of early-stage breast cancer, in particular the development of taxane-based regimens, have led to increased use of adjuvant chemotherapy. As a result, the decisions regarding the treatment of patients presenting with MBC have become more difficult, because many patients are likely to have received a variety of adjuvant chemotherapy regimens. The primary goal of treatment for MBC is palliation of disease--usually with prolongation of survival--with minimal toxicity. However, there is currently no "gold standard" in this setting, and the literature supports many choices for first- and second-line treatment. Other issues as yet unsettled in these patients are (1) whether to combine >or= 2 drugs or to use each drug alone until disease progression; (2) how to use novel targeted biologic agents; and (3) how to treat patients with HER2-overexpressing tumors after adjuvant treatment with trastuzumab. The role of taxanes, antimetabolites, and targeted agents in patients with MBC will be discussed in this review, particularly in the context of previous adjuvant therapy. The controversy surrounding the use of doublet or sequential therapy will also be discussed. Although considerable advances have been made toward answering these questions, many additional uncertainties have arisen, and further well-designed randomized studies are needed.