Survival analysis using neoadjuvant rectal score in patients with locally advanced rectal cancer who underwent surgery after neoadjuvant chemoradiotherapy: An ambispective study.

172 Background: Colorectal cancer, the third most common malignancy and a major cause of cancer deaths, is treated using a standard protocol of neoadjuvant chemoradiotherapy (NACTRT) or short-course radiotherapy (SCRT) followed by total mesorectal excision (TME) for locally advanced rectal cancers (LARC). Long-term follow-up is essential to determine study endpoints, necessitating surrogate markers for short-term outcomes. This study aims to stratify patients into risk groups based on their Neoadjuvant Rectal Cancer (NAR) score and evaluate its predictive value for oncological outcomes, including overall survival, disease-free survival (DFS), locoregional relapse-free interval (LRFI), and distant metastasis-free interval (DMFI), while also correlating clinicopathological characteristics with these outcomes. Methods: This ambispective observational study at the Regional Cancer Centre, Thiruvananthapuram, involved 459 patients with biopsy-proven, locally advanced rectal adenocarcinoma (T3/T4 and/or node positive) who underwent long-course neoadjuvant chemoradiotherapy (NACTRT) followed by curative surgery (Anterior Resection or Abdomino-Perineal Resection) between 2010 and 2015, with a minimum follow-up of three years. Exclusion criteria included previous malignancies, synchronous colorectal cancers, oligometastatic disease, and loss to follow-up. The study aimed to determine the predictive value of the Neoadjuvant Rectal Cancer (NAR) score for oncological outcomes. Clinicopathological details were collected from case records, imaging, and operative notes, and postoperative histopathological records were used to calculate the NAR score. Patients were categorized into three groups based on their NAR scores and followed prospectively for recurrence or death. Data were analyzed using frequency, percentages, mean, standard deviation, Chi-square test, Kaplan-Meier method, log-rank test, and Cox regression analysis, with a significance level set at p < 0.05. Results: 459 patients were included in the study, with 41.4% females, and 44% being less than 60 years. Most of the patients had lesion 5-10 cm from anal verge (46%). 77% of patients had T3 disease prior to the start of NATCTRT. 51.9% had underwent APR, and 80.4% had open surgery. 11.1% had PCR attained. 27% had disease recurrence of which most were distant metastasis. NAR was a significant predictor of overall survival, disease free survival, distant metastasis free interval and locoregional failure free interval. Other significant predictors of overall survival were pre-NACTRT T stage, pN stage, PLNR, CRM status and PCR, but only NAR was found to be significant on multivariate analysis. Conclusions: NAR score is a significant predictor of OS, DFS,LRFI and DMFI and can be used as a short term surrogate for survival data in anticipated trials.