Novel Cytotoxic Agents in the Treatment of Metastatic Breast Cancer

Evolving approaches to metastatic breast cancer patients pre-treated with anthracycline and taxane

Metastatic breast cancer is currently incurable and the goals of therapy focus on prolonging survival and maintaining quality of life by controlling symptoms and minimizing toxicity. Treatments for metastatic breast cancer include chemotherapeutic agents from various classes, such as taxanes, vinca alkaloids, anthracyclines and antimetabolites. This review provides an overview of chemotherapeutic agents for the treatment of metastatic breast cancer patients previously treated with anthracyclines and taxanes, focusing on a clinical evaluation of eribulin, the most recently approved agent for the treatment of metastatic breast cancer. Eribulin is a synthetic derivative of halichondrin B, a tumour growth inhibitor found in marine sponges, which prevents microtubule growth and sequesters the tubulin molecules into unusual aggregates, initiating apoptosis. Studies of eribulin have shown that the drug is effective in the treatment of previously treated metastatic breast cancer, and has an acceptable toxicity profile. Importantly, in the phase III EMBRACE study, eribulin treatment resulted in a survival advantage, a difficult endpoint to achieve with a single chemotherapeutic agent. An additional phase III study showed that eribulin has similar efficacy to capecitabine in women treated with no more than three prior therapies. Furthermore, pre-specified exploratory analyses suggest that particular patient subgroups may have greater therapeutic benefit with eribulin and may warrant further study to explore the potential mechanisms.