Prognostic ability of the neoadjuvant rectal (NAR) score in long‐course concurrent chemoradiotherapy for patients with locally advanced rectal cancer: a retrospective cohort study

Background: The aims of this study were to evaluate the prognostic ability of the neoadjuvant rectal (NAR) score and to develop and validate a nomogram based on the NAR for patients with locally advanced rectal cancer (LARC) treated with neoadjuvant chemoradiotherapy (nCRT). Methods: In total, 307 patients, including 230 patients from the primary cohort and 77 from the external cohort, were enrolled across the two centers. The associations of the NAR score with the tumor response, tumor control, and clinicopathological parameters were analyzed. Survival analysis was performed in the primary and external cohorts using Kaplan‒Meier curves. Univariate and multivariate analyses were performed to evaluate the prognostic factors. The NAR‐based nomogram was developed in the primary cohort and validated in the external cohort using the concordance index (C‐index), calibration plots, and decision curve analyses (DCAs). Results: Kaplan‒Meier survival analysis revealed that the disease‐free survival (DFS) and overall survival (OS) of the NAR > 16 group were significantly lower than those of the NAR ≤ 16 group (p < 0.001). Multivariate Cox regression analysis identified the NAR score as an independent prognostic factor for both DFS (hazard ratio [HR] = 2.484, 95% confidence interval [CI]: 1.159−5.323, p = 0.019) and OS (HR = 4.633, 95% CI: 1.076−19.941, p = 0.04). Calibration plots and DCAs showed that NAR‐based nomograms for DFS and OS were consistent and useful in clinical practice. Moreover, the C‐indexes of the NAR‐based nomograms were better than those of the other variables in both the primary and external cohorts. Conclusion: Our study validates the prognostic role of the NAR score for DFS and OS. The NAR‐based nomogram for OS could accurately predict the outcome of LARC patients by stratifying the risk score accordingly.