• ESGAR guidelines
• MRI imaging
• Rectal cancer
• staging

Purpose
The aim of this study is to compare the 2012 and 2016 structured MRI report templates proposed by the ESGAR for the TN staging of rectal cancer; to evaluate the role of DWI both in TN staging and yTN restaging of rectal cancer and in the assessment of CRM in primary staging and restaging.
Methods and Materials
Fifty-six patients affected by biopsy-proven rectal cancer were included in this retrospective study. Thirty-one out of fifty-six had undergone neoadjuvant chemoradiation therapy (nCRT) before surgery instead twenty-five patients underwent immediately to surgical treatment without CRT. All patients performed MR examination before surgery. Following surgery, operative specimens were analysed by a pathologist and the surgical resection specimen was used as standard of reference for determination of T and N stage, Mesorectal Fascia status and Extramural Vascular Invasion (EMVI).
Results
As regards the group of patients who didn’t undergo nCRT there is a moderate agreement between MRI-T Stage and the standard of reference for the expert reader according to 2012 guidelines while there is a good agreement according to 2016 ESGAR guidelines and a moderate agreement according to both 2012 and 2016 ESGAR guidelines for the resident. As regards N Stage there is a moderate agreement between MRI staging and the standard of reference for the expert reader according to both guidelines while there is a poor agreement for the resident according to 2012 ESGAR guidelines and a fair agreement according to 2016 ESGAR guidelines. As regards MRF status there is a very good agreement between MRI staging and the standard of reference for the two readers according to both guidelines. Finally, as regards EMVI the agreement is moderate for the expert reader and fair for the resident. As regards the group of patients who underwent nCRT there is a moderate agreement between MRI-T Stage and the standard of reference for the expert reader according to both guidelines; there is a fair agreement for the resident according to 2012 ESGAR guidelines and a moderate agreement according to 2016 ESGAR guidelines. As regards N Stage there is a moderate agreement between MRI staging and the standard of reference for the expert reader according to both guidelines while there is a fair agreement for the resident according to 2012 ESGAR guidelines and a moderate agreement according to 2016 ESGAR guidelines. As regards MRF status there is a poor agreement between MRI staging and the standard of reference for the expert reader according to both guidelines while there is a fair agreement for the resident according to both 2012 and 2016 guidelines. Finally, as regards EMVI the agreement is fair for the expert reader while there is no agreement for the resident.
Conclusion
Our data confirm that MRI has a crucial role in the staging and restaging of rectal cancer. Both 2012 and 2016 ESGAR structured MRI report templates are reliable tools to assess the radiological T and N stage of rectal cancer, especially for non-expert readers. The 2016 report template is more accurate in estimating T and N stage in the primary staging group, whereas no significant improvement was observed in the Restaging group of patients.