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Updated: May 10, 2026
Robot-assisted Total Mesorectal Excision and Lateral Pelvic Lymph Node Dissection for Locally Advanced Middle-low Rectal Cancer
Published on: February 12, 2022
Multicenter Evaluation of Rectal cancer ReImaging pOst Neoadjuvant (MERRION) Therapy
Ann M Hanly1, Elizabeth M Ryan, Ailín C Rogers
1*Centre for Colorectal Disease, St Vincent's University Hospital, Elm Park, Dublin, Ireland †Beaumont Hospital, Dublin, Ireland ‡University of Minnesota Medical Center, Minnesota, Minneapolis, MN.
Objective:
The aim of this study was to evaluate the utility of reimaging rectal cancer post-CRT (chemoradiotherapy) with magnetic resonance (MR) imaging of the pelvis for local staging and computed tomography of thorax, abdomen, and pelvis (CT TAP) to identify distant metastases.
Background:
The success of neoadjuvant CRT for locally advanced rectal cancer has changed an already complex management algorithm. There is no consensus whether patients should be restaged before surgery.
Methods:
Data from 5 institutions with prospectively maintained databases including patients who received neoadjuvant CRT for locally advanced rectal cancer were acquired. Only patients who had been staged pre- and post-CRT with MR imaging and CT TAP were included. MR findings were correlated with histopathological stage using weighted κ (kappa) statistics to test agreement, where a κ value of less than 0.5 was deemed unacceptable.
Results:
A total of 285 patients fulfilled the criteria for the study; 84% had American Joint Committee for Cancer stage 3 disease pre-CRT, and the remainder had stage 2 disease. Fourteen patients did not proceed to surgery post-CRT-2 were observed as "complete responders," and the remainder either had unresectable disease or were unfit for surgery. MR imaging could not predict T stage (κ = 0.212) or nodal involvement (κ = 0.336). Most pertinently, MR imaging was unable to detect a complete pathological response (κ = 0.021), nor could it discriminate T4 disease (κ = 0.445). CT TAP restaging altered management in 6.7% of patients, who had metastatic disease.
Conclusions:
MR reimaging using standard protocols is of limited value in determining surgical approaches; a better modality of local restaging is required.
