Introduction: In patients with locally advanced rectal cancer, restaging pelvis magnetic resonance imaging (MRI) after neoadjuvant concurrent chemoradiotherapy is recommended despite its limited accuracy in predicting pathologic T (ypT) and N (ypN) stage. Neoadjuvant rectal (NAR) score is a novel short-term surrogate endpoint for disease-free survival (DFS) and overall survival (OS). We tested the agreement between restaging MRI T (yT) and N (yN) with ypT and ypN stages, respectively, and explored the prognostic significance of restaging MRI NAR (mNAR) score.
Patients and methods: Between 2014 and 2018, 43 patients with locally advanced rectal cancer completed neoadjuvant concurrent chemoradiotherapy, had a restaging MRI, and underwent surgery. Weighted kappa was used to test the agreement between yT and yN with ypT and ypN, respectively. A kappa value of less than 0.5 was deemed unacceptable. Paired t test was used to compare NAR and mNAR mean scores. Survival was estimated by Kaplan-Meier curves.
Results: Restaging MRI could not predict ypT stage (slight agreement, κ = 0.111) or ypN stage (fair agreement, κ = 0.278). The mean mNAR score was higher than the mean NAR score (20 vs. 16, P = .0079). The median DFS for patients with low-intermediate NAR and high NAR was not reached vs. 30 months (P = .0063). The median OS for patients with low-intermediate NAR and high NAR was not reached vs. 40 months (P = .0056). There was a trend for longer DFS and OS in patients with low-intermediate mNAR scores (not reached in both groups, P = .058) compared to patients with high mNAR scores (not reached in both groups, P = .15).
Conclusion: Restaging MRI could not predict ypT and ypN stage. The mean mNAR score was higher than the mean NAR score. There was a trend for longer DFS and OS in patients with low-intermediate mNAR scores compared to patients with high mNAR scores.
Keywords: MRI; NAR; Neoadjuvant rectal score; Prognostic significance; Surrogate endpoint.
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