Endoscopic and MRI response evaluation following neoadjuvant treatment for rectal cancer: a pictorial review with matched MRI, endoscopic, and pathologic examples

A nonoperative management strategy, or Watch-and-Wait, following neoadjuvant therapies of locally advanced rectal adenocarcinoma is increasingly considered for select patients. Yet, standardized tumor response assessment to best select and surveil suitable patients remains an unmet clinical challenge. Endoscopic and MRI currently provide the most reliable tumor response estimations. However, resources illustrating variable tumor responses to neoadjuvant therapies remain limited. This pictorial review aims to provide detailed and annotated examples of common endoscopic and MRI findings of rectal cancer treatment response, while also emphasizing their respective diagnostic shortcomings and consequently, the necessity for a multidisciplinary approach to optimally manage these patients.