[Application of magnetic resonance imaging in TN re-staging and efficacy evaluation after neoadjuvant therapy for rectal cancer].

Neoadjuvant chemoradiotherapy (NCRT) combined with total mesorectal excision (TME) has become the recommended standard treatment strategy for local advanced rectal cancer (cT3 or cN+). After neoadjuvant chemoradiotherapy, preoperative T/N re-staging and efficacy evaluation of rectal cancer are directly related to the available treatment options and prognosis, so they are the common questions concerned by physicians. At present, magnetic resonance imaging (MRI) is acknowledged to be one of the more effective and feasible methods of T/N re-staging and efficacy evaluation, especially in the molecular microscopic scale. The diffusion weighted imaging (DWI) can reflect the movement of water molecules outside the tumor cells, and the multi-phase dynamic contrast enhanced MRI (DCE-MRI) can indirectly reflect the permeability of tumor vascular wall and local blood perfusion of tumor from the view of pathophysiological point. Because of the influence of edema, inflammatory response and fibrous tissue proliferation after radiotherapy, scholars both at home and abroad increasingly pay more attentions to the accuracy of T/N re-staging and efficacy prediction in MRI following neoadjuvant therapy. In this review, we elucidate the application value and limitation of MRI based on T/N re-staging and local efficacy evaluation.