Value of magnetic resonance imaging in assessing the efficacy of neoadjuvant chemoradiotherapy for locally advanced rectal cancer

Abstract

Before and after neoadjuvant chemoradiotherapy, overall and accurate evaluation of locally advanced rectal cancer is associated with the selection of treatment schedule, while imaging diagnosis is the key point. Anatomical and functional MRI has been applied in the prediction and assessment of neoadjuvant chemoradiotherapy efficacy for locally advanced rectal cancer. Before neoadjuvant chemoradiotherapy, distance of ≤ 5 cm from the lower margin to anal verge and extramural venous invasion status assessed by high resolution MRI are independent predictors of tumor response to neoadjuvant chemoradiotherapy. After neoadjuvant chemoradiotherapy, MRI assessment of tumor regression grade (TRG) is a valuable imaging indicator to evaluate the response to neoadjuvant chemoradiotherapy. Furthermore, FDG PET, diffusion weighted imaging and dynamic contrast enhanced MRI can be used to evaluate the efficacy based on tumor cell metabolism, tumor cell density and tumor blood perfusion respectively, which provides helpful supplement for high resolution MRI based on anatomy.