Prognostic significance of neoadjuvant rectal score in locally advanced rectal cancer after neoadjuvant chemoradiotherapy and construction of a prediction model

Aim: To evaluate the prognostic significance of neoadjuvant rectal (NAR) score after neoadjuvant chemoradiotherapy (nCRT) for locally advanced rectal cancer (LARC), and to develop a nomogram predicting disease-free survival (DFS). Method: A total of 522 LARC patients undergoing nCRT and surgery were included. NAR scores were calculated using the equation [5pN-3(cT-pT)+12](boolean AND)2/9.61, and classified as low (< 8), intermediate (8-16), and high (> 16). Clinicopathological and survival outcomes were compared. Cox regression analysis was performed to identify risk factors of DFS. A predicting nomogram was developed and validated internally. Results: For NAR score classification, 193 (37.0%) were low, 183 (35.0%) were intermediate, and 146 (28.0%) were high. Higher NAR score was associated with fewer pCR, lower tumor regression grade (TRG), and higher ypTNM stage. A total of 5-year DFS for low, intermediate, and high NAR groups was 85.6%, 71.9%, and 47.2%, respectively (P < 0.001). NAR score (HR=2.488, P=0.002), TRG (HR=2.811, P=0.047), CRM involvement (HR=2.703, P=0.002), and IMA nodal metastasis (HR=2.441, P=0.001) were independent prognostic factors of DFS. A predicting nomogram was developed with C-index of 0.701. Conclusion: NAR score could help in predicting DFS after nCRT. A nomogram was developed to identify subpopulations with aggressive tumors during clinical decision-making.