The role of magnetic resonance imaging on evaluating response of neoadjuvant therapy for breast cancer

Breast magnetic resonance imaging (MRI) is always considered to be more accurate for evaluating neoadjuvant therapy (NAT) response than mammography, ultrasound and clinical examination. Preoperative MRI aims to evaluate residual disease to facilitate surgical planning. MRI scans performed before and/or during NAT aim to predict the treatment response and thus adjust the NAT plan at an early stage. MRI accuracy depends on tumor morphology, histology, shrinkage pattern and molecular subtype. Combining multiparameter functional MRI can improve the prediction accuracy. In addition, radiomics offers high-dimensional and high-throughput signatures and were shown to predict treatment response before NAT. This article reviews the indicators of breast MRI for evaluating NAT response, including morphological MRI features, enhancement and pharmacokinetic parameters, apparent diffusion coefficient (ADC), choline concentration, etc., even radiomic signatures and illustrates their advantages, limitations and future directions.