Role of magnetic resonance imaging in the evaluation of rectal cancer after neoadjuvant therapy.

The management of locally advanced rectal cancer is rapidly evolving and is adapted according to the response to neoadjuvant therapy (NAT). This allows clinicians to tailor strategies for patients with favourable responses, including the possibility of preserving the rectum or of reducing complications associated with a surgery that carries a high-risk for morbidity. Radiologists can have a key influence on decision making through MRI, which characterises patterns of response and post-treatment changes to the tumour as well as other prognostic elements such as lymph nodes, extramural vascular invasion, tumour deposits and mesorectal fascia involvement. However, imaging findings can be difficult to interpret, requiring a thorough understanding of both the findings and the current limitations of MRI. In this review, we address the rationale supporting the paradigm shift towards organ preservation strategies, and the role and current challenges of MRI in the restaging of rectal cancer after NAT.