e15166 Background: In patients with locally advanced rectal adenocarcinoma (LARA), the response to neoadjuvant concurrent chemoradiation (NCCR) correlates with long-term outcomes. Neoadjuvant rectal (NAR) score ([5 ypN - 3 (cT - ypT) + 12]2/9.61) is a novel short-term surrogate endpoint for disease free survival (DFS) and Overall survival (OS). The prognostic significance of magnetic resonance imaging (MRI) findings following NCCR is yet to be explored. Here, we evaluated the agreement between post NCCR MRI yT and yN and pathological ypT and ypN. In addition, we calculated the post NCCR MRI NAR (mNAR) score using the MRI yT and yN ([5 yN - 3 (cT - yT) + 12]2/9.61) and explored its prognostic significance. Methods: Between 2014 and 2018, all patients with LARA were identified. Among those, 43 patients received NCCR, had post NCCR MRI and underwent surgical resection. Weighted Kappa was used to measure the agreement between post NCCR MRI yT and yN and pathological ypT and ypN. Paired t-test was used to compare the means between NAR and mNAR scores. NAR and mNAR scores were classified as low ( < 8), intermediate (8-16) and high ( > 16). DFS and OS were analyzed using Kaplan-Meier curves. Results: In our cohort, the agreement was slight between post NCCR MRI yT and Pathological ypT (p = 0.111), and fair between post NCCR MRI yN and pathological ypN (0.278). The mean NAR score was 16 and the mean mNAR score was 20 (p = 0.0079). Low-intermediate and high NAR scores were seen in 31 (72%) and 12 (28%) patients respectively. However, low-intermediate and high mNAR scores were seen in 20 (47%) and 23 (53%) patients respectively. The median DFS in patients with low-intermediate and high NAR scores was not reached and 30 months (p = 0.00063) respectively. The median OS in patients with low-intermediate and high NAR scores was not reached and 40 months (p = 0.00056) respectively. The median DFS in patients with low-intermediate and high mNAR scores was not reached in both groups (p = 0.058). The median OS in patients with low-intermediate and high mNAR scores was not reached in both groups (p = 0.15). Conclusions: Post NCCR MRI yT and yN had slight and fair agreements with ypT and ypN respectively. In our cohort, there was a difference between NAR and mNAR. NAR demonstrated prognostic significance for DFS and OS, while mNAR did not at the time of analysis.