Modern MR Imaging Technology in Rectal Cancer; There Is More Than Meets the Eye

Abstract

MR imaging (MRI) is now part of the standard work up of patients with rectal cancer. Restaging MRI has been traditionally used to plan the surgical approach. Its role has recently increased and been adopted as a valuable tool to assist the clinical selection of clinical (near) complete responders for organ preserving treatment. Recently several studies have addressed new imaging biomarkers that combined with morphological provides a comprehensive picture of the tumor. Diffusion-weighted MRI (DWI) has entered the clinics and proven useful for response assessment after chemoradiotherapy. Other functional (quantitative) MRI technologies are on the horizon including artificial intelligence modeling. This narrative review provides an overview of recent advances in rectal cancer (re)staging by imaging with a specific focus on response prediction and evaluation of neoadjuvant treatment response. Furthermore, directions are given for future research.

Keywords: MR imaging; artificial intelligence; functional imaging; organ preservation; rectal cancer.

FIGURE 1

Three-modality approach with combination of T2W-MRI, DWI, and endoscopy of the selection of a patient with a clinical complete response. A low rectal tumor is seen on MRI (A, B). On restaging MRI 8 weeks after completion of chemoradiotherapy (C) only minimal fibrosis (yellow arrow) is seen anteriorly in the rectal wall. On restaging DWI (D) there is absence of high diffusion signal (yellow arrow). Clinical assessment by endoscopy (E) reveals a white scar with telangiectasia (yellow arrow).