Management of metastatic breast cancer: monotherapy options for patients resistant to anthracyclines and taxanes.

Resistance to chemotherapeutic agents is a significant obstacle to the effective treatment of metastatic breast cancer (MBC). Anthracycline- and taxane-based regimens are active as first-line treatment for MBC; however, MBC often progresses because of primary or acquired resistance to anthracyclines and taxanes. There are few options for the treatment of patients with anthracycline- and taxane-resistant or taxane-refractory MBC. This article reviews several single agents that have demonstrated activity as treatment for patients with MBC who progress during, or rapidly following, treatment with anthracyclines and taxanes. Results from clinical trials evaluating agents such as ixabepilone, albumin-bound paclitaxel, capecitabine, vinorelbine, pemetrexed, and irinotecan are presented. Single-agent capecitabine is approved for the treatment of patients after failure of anthracyclines and taxanes. Ixabepilone has demonstrated efficacy in patients with MBC resistant to multiple chemotherapeutic agents and is the only agent approved by the Food and Drug Administration as monotherapy for anthracycline-, taxane-, and capecitabine-resistant MBC. Improved treatment strategies and further evaluation of newer agents may reduce the current burden of treatment-resistant or treatment-refractory MBC.