The history, present situation, and future directions of neoadjuvant chemotherapy for HER2-negative breast cancer.

Chemotherapy has played a significant role in breast cancer therapy and dramatically improved the outcome of breast cancer patients. Neoadjuvant chemotherapy (NAC) is defined as chemotherapy conducted before surgery. The rationale for NAC in operable breast cancer is that the benefit of systemic chemotherapy on the long-term prognosis does not change, regardless of whether chemotherapy is conducted before or after surgery. NAC is now widely used for early and advanced breast cancer patients since it has two significant advantages over conventional adjuvant chemotherapy after surgery. One is that the rate of the breast-conserving surgery increase resulted from tumor shrinkage during NAC, which can contribute to a minimal invasion from surgical therapy and good quality of life following therapy. Another is that a response to chemotherapy can be observed in in-vivo setting. Patients who achieve the pathological complete response (pCR) show a favorable prognosis. Thus, the response to NAC can be used as an indicator for personalized medicine. To date, novel agents for NAC have been explored in randomized trials, setting the pCR rate as an endpoint. Also, response- and residual disease-guided therapy have been ready for prime time in daily practice. The author describes the history, current situation, and future direction of NAC for HER2-negative breast cancer in the review article.