[The Role of Preoperative Chemotherapy Depending on Breast Cancer Subtype].

Following the discovery that the prognostic impact of preoperative chemotherapy depends on the primary breast cancer subtype, the treatment strategy for primary breast cancer changed. Pathologic complete response(pCR)with preoperative chemotherapy is predictive of a favorable prognosis in patients with HER2 type or triple-negative type breast cancer, but not in patients with ER-positive/HER2-negative, the so-called Luminal type, breast cancer. However, the role of preoperative chemotherapy in patients with Luminal-B type breast cancer who may need chemotherapy should be further assessed. Recent studies have reported severalsubtypes of triple-negative breast cancer, distinguishable by gene expression analysis, which may respond differently to treatment. Furthermore, novel agents, including pertuzumab or T-DM1 for HER2 type breast cancer, bevacizumab or PARP inhibitors for triple negative-breast cancer, or combination regimens with these novelagents, are expected to achieve higher pCR rates and improve patient prognosis. The tumor microenvironment may also play an important role in predicting treatment response or prognosis. It is important that tailor-made treatment strategies for patients with primary breast cancer, especially for patients who will not respond favorably to current standard therapies, consider both the treatment effects and the medicaleconomic effects.