Impact of total lymph node count and lymph node ratio on staging and survival after pancreatectomy for pancreatic adenocarcinoma: a large, population-based analysis.

Background: Based on data from other malignancies, the number of lymph nodes evaluated and the ratio of metastatic to examined lymph nodes (LNR) may be important predictors of survival. LNR has never been investigated in a large population-based study of patients with pancreatic adenocarcinoma.
Methods: The Surveillance, Epidemiology, and End Results (SEER) database was used to identify 4005 patients who underwent resection for pancreatic adenocarcinoma from 1988 to 2003. The effect of total lymph node count and LNR on survival was examined using univariate and multivariate analyses.
Results: The median number of lymph nodes examined was seven; 390 (10.1%) patients had no lymph nodes examined. Of those patients who had at least one lymph node examined, 1507 (43.3%) had no lymph node metastases (N0) and 1971 (56.7%) had metastatic nodal disease (N1). Overall median survival was 13 months, and 5-year survival was 6.8%. N1 disease was associated with a worse 5-year survival compared with N0 disease (4.3 vs 11.3%, respectively, P < .001). Patients with N0 disease could be further stratified based on the number of lymph nodes evaluated (median survival: 1-11 nodes, 16 months vs 12 or more nodes, 23 months; P < .001). For N1 patients, LNR was one of the most powerful factors associated with survival (LNR > 0-0.2, 15 months; LNR > 0.2-0.4, 12 months; LNR > 0.4, 10 months) (P < .001).
Conclusions: Most patients have an inadequate number of lymph nodes evaluated following pancreatic surgery. N0 patients who have fewer than 12 lymph nodes examined may be understaged. In patients with N1 disease, LNR may better substratify patients with regard to prognosis.