Role of imaging in neoadjuvant therapy for breast cancer.

Neoadjuvant chemotherapy (NAC) involves administration of chemotherapeutic agents to patients with newly diagnosed breast cancer prior to definitive surgical treatment. Assessment of disease response to chemotherapeutic agents in vivo prior to any surgical intervention is necessary as medical oncologists are commonly tailoring or changing therapy during NAC based on response. It can also maximize the pathologic complete response (pCR) rate, resulting in more women undergoing breast conservation rather than mastectomy. Although some studies show a pCR to NAC in only 13-26 % of women, recent studies have shown higher pCR rates, especially for HER2-positive disease treated with targeted anti-HER2 therapy. Thus, accurate imaging tools for quantifying disease response are critical in the evaluation and management of patients undergoing NAC. There is currently no standard imaging method for monitoring response to therapy. Response to therapy tends to vary by tumor subtype and can be accurately assessed on imaging. We review the role of imaging before and after neoadjuvant therapy and discuss the advantages and limitations of currently available modalities, including mammography, ultrasonography, magnetic resonance imaging, and nuclear imaging.