MRI at Restaging after Neoadjuvant Therapy for Rectal Cancer Overestimates Circumferential Resection Margin Proximity as Determined by Comparison with Whole-Mount Pathology.
Academic Article
Overview
abstract
BACKGROUND: Current guidelines recommend restaging with MRI after neoadjuvant therapy for rectal cancer, but the accuracy of restaging MRI in estimating circumferential margin involvement requires additional clarification. OBJECTIVE: Measure the accuracy of circumferential resection margin assessment by MRI after neoadjuvant therapy and identify characteristics associated with accuracy. DESIGN: MRI data were retrospectively analyzed for concordance with the findings of whole-mount pathology analysis of the corresponding surgical specimens. Univariate and multivariate logistic regression analyses were performed to identify characteristics associated with accuracy. SETTING: Comprehensive cancer center. PATIENTS: Consecutive patients who underwent total mesorectal excision for rectal cancer between January 2018 and February 2020 after receiving neoadjuvant therapy and undergoing restaging with MRI. MAIN OUTCOME MEASURES: Accuracy, sensitivity, specificity, and positive and negative predictive values for categorizing the circumferential resection margin as threatened; Mean and paired mean differences in proximity of the margin. RESULTS: Of the 94 patients included in the analysis, 39 (41%) had a threatened circumferential resection margin according to MRI at restaging, but only 17 (18%) had a threatened margin based on pathology. The accuracy of MRI in identifying a threatened margin was 63.8%, with margin proximity overestimated by 0.4 cm on average. In multivariate logistic regression, anterior location of the margin and tumor proximity to the anal verge were independently associated with reduced MRI accuracy. LIMITATIONS: Retrospective design, single institution. CONCLUSIONS: The knowledge that MRI-based restaging after neoadjuvant therapy overestimates circumferential margin proximity may render some surgical radicality unnecessary and thereby help avoid the associated morbidity. With the recognition that MRI-based assessment of margin proximity may not be reliable for an anterior margin and for distal tumors, radiologists may want to use greater caution in interpreting images of tumors with these characteristics and to acknowledge the uncertainty in their reports. See Video Abstract at http://links.lww.com/DCR/B814 .
