Neoadjuvant Chemotherapy and Targeted Therapy in Breast Cancer: Past, Present, and Future

Traditionally, neoadjuvant treatment for breast cancer was preserved for locally advanced and inflammatory disease, converting an inoperable to a surgical resectable cancer. In recent years, neoadjuvant therapy has become an accepted treatment option also for lower tumor stages in order to increase the rate of breast conserving therapy and to reduce the extent of surgery. Furthermore, treatment response can be monitored, and therefore, patient compliance may be increased. Neoadjuvant trials, additionally, offer the opportunity to evaluate new treatment options in a faster way and with fewer patients than large adjuvant trials. Compared to the metastatic setting, the issue of acquired resistance and pretreatments, which may distort treatment efficacy, can be avoided. New trial designs like window-of-opportunity trials or postneoadjuvant trials provide the chance to identify tumor sensitivity or to overcome tumor resistance in early tumor stages. In particular, in HER2-positive breast cancer, the neoadjuvant approach yielded great successes. The dual HER2 blockade with trastuzumab and pertuzumab recently showed the highest pCR rates ever reported. Many new drugs are in clinical testing with the aim to further increase pCR rates. Whether this endpoint really represents a surrogate for long-term outcome is not answered yet and will be discussed in this review.