Impact of Lymph Node Ratio on Survival Outcome in Esophageal Squamous Cell Carcinoma After Minimally Invasive Esophagectomy.

Esophageal squamous cell cancer (ESCC) is one of the deadliest cancers in the world. Esophagectomy remains the principal treatment, and minimally invasive esophagectomy (MIE) has been performed worldwide. This study aimed to clarify whether the lymph node ratio (LNR), defined as the ratio of metastatic lymph nodes (LNs) to examined, is a prognostic factor for ESCC after MIE. This study included 327 MIEs with the patient in the prone position at two institutions from 2010 to 2015. Cox proportional hazards regression analyses using clinicopathologic characteristics and the LNR were performed for the pN1 patients and the whole cohort. In the multivariate analysis for all stages, independent prognostic factors were depth of tumor invasion (P < 0.0001), LNR (P = 0.014), operative time (P = 0.003), and pneumonia (P = 0.012). In the analysis of the pN1 subgroup, the optimum LNR cutoff level for overall survival (OS) was 9 based on receiver operation characteristic analysis. The LNR was significantly associated with depth of tumor invasion (P = 0.004) and number of metastatic LNs (P < 0.0001). The OS curve for the group with an LNR of 9 or higher was significantly worse than for the group with an LNR lower than 9 (P < 0.001). Multivariate analyses demonstrated that the LNR is a unique independent prognostic factor for the pN1 subgroup (hazard ratio, 6.811; 95% confidence interval, 2.009–23.087; P = 0.002). The LNR is an independent prognostic factor in ESCC after MIE. Especially for patients with pN1 status, the LNR is more useful than the number of metastatic LNs for predicting survival outcome.