Targeted therapies for the treatment of breast cancer in the post-trastuzumab era

Targeted therapies for breast cancer are evolving rapidly. Trastuzumab has revolutionized breast cancer treatment and outcome, reducing the risk for recurrence and significantly increasing survival, at least for a subgroup of patients. Other targeted therapies, such as bevacizumab, a monoclonal antibody targeting angiogenesis, lapatinib, a dual human epidermal growth factor receptor (HER)-1 and HER-2 inhibitor, other small-molecule tyrosine kinase inhibitors, and mammalian target of rapamycin inhibitors, have been developed in phase II and III clinical trials. Although there has been rapid approval of these new drugs by health authorities, some questions have emerged about their application in clinical practice. What is the appropriate drug or sequence of drugs? What is the ideal target? How should tumor response be evaluated? Are financial resources sufficient to treat patients? How do we design trials with these molecules? These are emerging as current dilemmas for clinical oncologists.