Greater lymph node retrieval and lymph node ratio impacts survival in resected pancreatic cancer

Background Surgical resection is the mainstay of pancreatic cancer treatment; however, the ideal lymphadenectomy remains unsettled. This study sought to determine whether number of examined lymph nodes (eLNs) and lymph node ratio (LNR) impact survival. Methods The U.S. National Cancer Data Base (2003-2011) was reviewed for patients who underwent initial resection for clinical stage I and II pancreatic adenocarcinoma. Univariate and multivariate survival analyses were performed. Results Of 14,007 patients, 15.6% had 0-6 eLN, 27.1% 7-12, 13.4% 13-15, and 38.6% > 15 eLN. Median eLN was 11 for pancreaticoduodenectomy, and 14 for distal, total pancreatectomy, or other procedure. ELN >15 was associated with significantly improved survival in both node negative and positive disease (P < 0.001, both). In multivariable analysis, 7-12, 13-15, and >15 eLN had improved survival relative to 0-6 eLN (HR 0.87, P < 0.001, HR 0.89, P = 0.002, HR 0.82, P < 0.001, respectively). A total of 34.5% of patients had an LNR of 0, 31.5% ≤ 0.2, 20.3% 0.2-0.4, 11.7% 0.4-0.8, and 2.0% had an LNR >0.8. Patients with LNR 0 had improved survival in T1-T3 disease (P < 0.01). In multivariable analysis, higher LNR was negatively associated with survival (LNR 0-0.2: HR 1.44, P < 0.001, LNR 0.2-0.4: HR 1.82, P < 0.001, LNR 0.4-0.8: 2.03, P < 0.001, LNR >0.8, P < 0.001). Even with suboptimal eLN (eLN ≤6 or ≤12), higher LNR remained an independent predictor of mortality. Conclusions Greater lymph node retrieval in stage I & II pancreatic adenocarcinoma may have prognostic value, even in node-negative disease. Lymph node ratio is inversely related to survival and may be useful with suboptimal eLN.