Natural and therapy-induced immunosurveillance in breast cancer

The immunosurveillance theory postulates that tumors evolve and progress in an uncontrolled fashion only when anticancer immune responses fail. Natural immunosurveillance clearly influences human breast cancer (BC) progression because the prognosis of BC patients is dictated by the density, composition and activity of the tumor immune infiltrate at diagnosis. Moreover, chemotherapeutic and radiotherapeutic regimens commonly employed for the treatment of BC affect the tumor immune infiltrate, and accumulating data suggest that the clinical efficacy of these treatments is largely determined by T cell-dependent tumor-specific immune responses. In addition, the mechanism of action of targeted anticancer therapeutics, such as the erb-b2 receptor tyrosine kinase 2 (ERBB2)-targeting agent trastuzumab, involves the innate and adaptive arms of the immune system. In this Review, we discuss these findings as well as preliminary evidence indicating that immunotherapy constitutes a promising option for the treatment of BC. Moreover, we point out that the successful implementation of immunotherapy to BC management requires the optimization of current immunotherapeutic regimens and the identification of immunological biomarkers that enable improved risk stratification and the design of personalized, dynamic treatment plans.