Adjuvant biologic agents for breast cancer

In the year 2013, a total of 234,580 new cases of breast cancer were diagnosed in the USA. Although the incidence of breast cancer is increasing, the 5-year survival rate has continued to improve. This improvement to overall survival (OS) is largely due to new chemotherapeutic and biologic agents. Biologic agents currently in use in early-stage breast cancer mainly target the human epidermal growth factor receptor 2 (HER2). HER2 belongs to the family of epidermal growth factor receptors (EGFRs) and is overexpressed in 20–30 % of all breast cancers. Further, the overexpression of HER2 is a negative prognostic and predictive factor. Patients with HER2+ breast cancers have more aggressive disease, a higher likelihood of lymph node involvement, decreased estrogen receptor (ER) expression, and increased resistance to endocrine therapy, while also found to have an increased responsiveness to anthracycline treatment. Initially approved by the Food and Drug Administration (FDA) in 1998 for treatment of HER2+ metastatic breast cancer, trastuzumab has been approved in the adjuvant setting after pivotal trials revealed a statistically significant reduction in the risk of recurrence by nearly 50 % and an improvement of overall survival (OS) by a third. Several other biologic agents are currently under investigation with the goal to improve the long-term survival in women with early-stage breast cancer.