Pathologic Lymph Node Ratio Is a Predictor of Survival in Esophageal Cancer

Background. A ratio between pathologic and examined lymph nodes may have predictive relevance in esophageal cancer. We sought to determine the prognostic value of lymph node ratio (LNR) compared with TNM and N stage using the seventh edition American Joint Commission on Cancer and International Union Against Cancer criteria. Methods. We abstracted data from 347 consecutive patients undergoing esophagectomy for esophageal cancer between 1999 and 2010 at our institution. Patients were stratified into surgery alone or induction therapy followed by surgery. Kaplan-Meier and Cox proportional hazard models estimated the survival function using LNR as a continuous variable or categorized into 0, more than 0.0 to less than 0.1, 0.1 to less than 0.2, 0.2 to less than 0.3, and 0.3 or greater. The influence of LNR on survival was assessed by the Wald chi(2) statistic and survival plots. Results. A total of 173 patients (49.9%) underwent induction therapy. The pathologic complete response rate was 55 of 173 (32%). The median number of examined nodes in surgery alone was 14 (interquartile range, 8 to 21), and induction was 12 (interquartile range, 7 to 17). Patients with nodal disease (n = 137) had a median LNR of 0.2 with equivalent survival regardless of induction therapy. Examination of LNR as a continuous variable demonstrated that LNR is an independent predictor of survival in both groups. After categorization, LNR contributed more toward estimating survival than pN stage in both groups. Conclusions. Lymph node ratio is an independent predictor of survival in patients undergoing esophagectomy for esophageal cancer. The LNR makes a greater contribution in estimating overall survival than pN stage, regardless of the utilization of induction therapy. (Ann Thorac Surg 2012;94:1643-51) (C) 2012 by The Society of Thoracic Surgeons