MRI restaging of rectal cancer: The RAC (Response–Anal canal–CRM) analysis joint consensus guidelines of the GRERCAR and GRECCAR groups

•The evaluation of tumor response in rectal cancer is a challenge for the radiologist.•The main features to evaluate can be summarized through the “RAC assessment: Response–Anal canal– Circumferential resection margin”.•The combination of functional and morphological tumor features on MRI helps assess rectal tumor response to neoadjuvant therapy.•After a near complete tumor response on MRI, another MRI evaluation at six to ten weeks is recommended to potentially propose a watch and wait approach. To develop guidelines by international experts to standardize data acquisition, image interpretation, and reporting in rectal cancer restaging with magnetic resonance imaging (MRI). Evidence-based data and experts’ opinions were combined using the RAND-UCLA Appropriateness Method to attain consensus guidelines. Experts provided recommendations for reporting template and protocol for data acquisition were collected; responses were analysed and classified as “RECOMMENDED” versus “NOT RECOMMENDED” (if ≥ 80% consensus among experts) or uncertain (if < 80% consensus among experts). Consensus regarding patient preparation, MRI sequences, staging and reporting was attained using the RAND-UCLA Appropriateness Method. A consensus was reached for each reporting template item among the experts. Tailored MRI protocol and standardized report were proposed. These consensus recommendations should be used as a guide for rectal cancer restaging with MRI.