Lymph node ratio is a more robust predictor of overall survival than N stage in stage III colorectal adenocarcinoma

Background Lymph node ratio (LNR) may offer superior prognostic stratification in colorectal adenocarcinoma compared with N stage. However, candidate cutoff ratios require validation. We aimed to study the prognostic significance of LNR and its optimal cutoff ratio. Methods We reviewed the pathology records of all patients with stage III colorectal adenocarcinoma who were managed at the King Hussein Cancer Center between January 2014 and December 2019. We then studied the clinical characteristics of the patients, correlates of lymph node count, prognostic significance of positive lymph nodes, and value of sampling additional lymph nodes. Results Among 226 included patients, 94.2% had ≥ 12 lymph nodes sampled, while 5.8% had < 12 sampled lymph nodes. The median number of lymph nodes sampled varied according to tumor site, neoadjuvant therapy, and the grossing pathologist’s level of training. According to the TNM system, 142 cases were N1 (62.8%) and 84 were N2 (37.2%). Survival distributions differed according to LNR at 10% ( p = 0.022), and 16% ( p < 0.001), but not the N stage ( p = 0.065). Adjusted Cox-regression analyses demonstrated that both N stage and LNR at 10% and 16% predicted overall survival ( p = 0.044, p = 0.010, and p = 0.001, respectively). Conclusions LNR is a robust predictor of overall survival in patients with stage III colorectal adenocarcinoma. At a cutoff ratio of 0.10 and 0.16, LNR offers better prognostic stratification in comparison with N stage and is less susceptible to variation introduced by the number of lymph nodes sampled, which is influenced both by clinical variables and grossing technique.