Introduction: The impact of the number of lymph node (LN) evaluated pathologically on accurate staging is unknown. Our primary aim was to determine a minimum number of evaluated LN needed to provide accurate staging of pancreatic cancer.
Methods: Four hundred ninety-nine patients underwent a curative pancreatectomy for pancreatic adenocarcinoma cancer from 1981-2007. The probability of understaging a patient as N0 was estimated based on the number of LN evaluated. The prognostic value of LN ratio (LNR) was assessed.
Results: Survival for node-negative (pN0) patients with <11 LN examined was worse than for pN0 patients with ≥11 LNs with a hazard ratio (95 % CI) of 1.33 (1.1-1.7, p = 0.01) with 3-year survivals of 32 vs. 50%, respectively. Three-year survival for pN1 patients with <11 nodes evaluated was similar to pN1 patients with ≥11 nodes (25 vs. 30%). LNR ≥ 0.17 predicted worse survival with hazard ratio of 1.76 (1.3-2.4, p = 0.001) than LNR < 0.17; 3-year survivals were 37 vs. 19%.
Conclusion: Patients with "N0" disease with <11 LN evaluated pathologically have worse survival, suggesting that metastatic nodes were missed by evaluating too few nodes. For pN1 patients, LNR stratifies survival of patient cohorts more accurately. Adequate staging of pancreatic cancer requires pathologic evaluation of ≥11 LNs.