Nodal Counts and Lymph Node Ratio Impact Survival After Distal Pancreatectomy for Pancreatic Adenocarcinoma

Background The number of lymph nodes required for accurate staging after distal pancreatectomy for pancreatic adenocarcinoma is unknown. Methods The Surveillance, Epidemiology, and End Results (SEER) database was used to identify 1,473 patients who underwent distal pancreatectomy for pancreatic adenocarcinoma from 1998 to 2010. We evaluated the influence of the total number of lymph nodes examined (NNE) and the lymph node ratio (LNR-positive nodes/total nodes examined) on survival. Results The median NNE was 8. No nodes were examined in 232 (16 %) of the patients, and 843 (57 %) had <10 NNE. Of the patients who had at least one node examined, 612 (49 %) were node positive. In the node-negative subset, the median and 5-year overall survival for patients with <= 10 NNE was significantly worse than patients with >10 NNE (16 vs. 20 months and 13 vs. 19 %, respectively, p<0.011). For node-positive patients, those with LNR <= 0.1 had better 5-year overall survival compared with LNR >0.1 (17 vs. 6 %, p=0.002). Discussion Patients with pancreatic cancer undergoing distal pancreatectomy should ideally have at least 11 lymph nodes examined to avoid understaging. For node-positive patients, LNR may be a better prognostic indicator than the total number of positive nodes.