Predicting response to chemoradiotherapy in rectal cancer via visual morphologic assessment and staging on baseline MRI: a multicenter and multireader study

Abstract

Purpose Pre-treatment knowledge of the anticipated response of rectal tumors to neoadjuvant chemoradiotherapy (CRT) could help to further optimize the treatment. Van Griethuysen et al. proposed a visual 5-point confidence score to predict the likelihood of response on baseline MRI. Aim was to evaluate this score in a multicenter and multireader study setting and compare it to two simplified (4-point and 2-point) adaptations in terms of diagnostic performance, interobserver agreement (IOA), and reader preference. Methods Twenty-two radiologists from 14 countries (5 MRI-experts,17 general/abdominal radiologists) retrospectively reviewed 90 baseline MRIs to estimate if patients would likely achieve a (near-)complete response (nCR); first using the 5-point score by van Griethuysen (1=highly unlikely to 5=highly likely to achieve nCR), second using a 4-point adaptation (with 1-point each for high-risk T-stage, obvious mesorectal fascia invasion, nodal involvement, and extramural vascular invasion), and third using a 2-point score (unlikely/likely to achieve nCR). Diagnostic performance was calculated using ROC curves and IOA using Krippendorf’s alpha (α). Results Areas under the ROC curve to predict the likelihood of a nCR were similar for the three methods (0.71–0.74). IOA was higher for the 5- and 4-point scores (α=0.55 and 0.57 versus 0.46 for the 2-point score) with best results for the MRI-experts (α=0.64-0.65). Most readers (55%) favored the 4-point score. Conclusions Visual morphologic assessment and staging methods can predict neoadjuvant treatment response with moderate–good performance. Compared to a previously published confidence-based scoring system, study readers preferred a simplified 4-point risk score based on high-risk T-stage, MRF involvement, nodal involvement, and EMVI. Graphical abstract

Nonoperative Management for Rectal Cancer

“…However, diffusion weighted MRI is prone to artifacts, which can introduce pitfalls for inexperienced readers. 43,44 Unlike the With current tools, up to 30% of complete responders are not identified at response assessment. 45,46 Thus, in selected patients, extending the waiting interval could be considered for patients who show a "near CR" at first response assessment to allow for further regression and help determine whether there is a cCR.…”

Advances in MRI-Based Assessment of Rectal Cancer Post-Neoadjuvant Therapy: A Comprehensive Review

“…Thus, establishing a correlation with the baseline rectal MRI stands as a highly beneficial practice, aiding in the precise determination of the tumor bed’s location [ 53 ]. Scar tissue should follow the same distribution and shape as the primary tumor [ 54 ]. This integrated approach enhances the accuracy of interpretation and minimizes the potential for misinterpretations.…”