Magnetic resonance imaging and neoadjuvant chemotherapy

Neoadjuvant chemotherapy (NAC) is now widely used internationally to provide improved surgical outcomes, recurrent free survival, and overall survival in certain subtypes of breast cancer. Therefore, the opportunity to monitor treatment response in vivo and as early in the treatment as possible to identify non-responders is critical. Early initiation of systemic therapy can improve overall and disease-free survival for patients with locally advanced breast cancer (LABC) or inflammatory cancer even though these patients usually receive mastectomies despite complete response after NAC. For non-responders, the sooner these patients are identified, the quicker changes to treatment plans can be made to identify a more ideal regimen for them in a timely manner. Physical examination, mammography, and sonography have all been used to assess the response to NAC, primarily by measuring the size of the residual tumor. Internationally, the 'Response Evaluation Criteria in Solid Tumors" (RECIST) is commonly used to standardize the assessment of response to therapy, based on the tumor size. Unfortunately size assessment does not take into account treatment-induced fibrosis or inflammation which can result in overestimation or underestimation of the residual disease. Magnetic resonance imaging (MRI) with intravenous contrast and advanced MRI techniques provide new opportunities for assessing tumor morphologic changes, tumor vascularity, tumor cellularity, and tumor metabolic features. MRI has been shown to be more accurate and reliable than physical examination, mammography, or sonography. The combination of contrast-enhanced MRI with diffusion-weighted imaging (DWI) and better understanding of tumor biology and genomics improve our ability to predict responders from non-responders. To date, there is still no consensus on the role of MRI for assessing response to NAC or on a standardized MRI examination in patients receiving NAC.