title: N0/N1, PNL, or LNR? The effect of lymph node number on accurate survival prediction in pancreatic ductal adenocarcinoma.
abstract: BACKGROUND
  We evaluated the prognostic accuracy of LN variables (N0/N1), numbers of positive lymph nodes (PLN), and lymph node ratio (LNR) in the context of the total number of examined lymph nodes (ELN).
  
  
  METHODS
  Patients from SEER and a single institution (MGH) were reviewed and survival analyses performed in subgroups based on numbers of ELN to calculate excess risk of death (hazard ratio, HR).
  
  
  RESULTS
  In SEER and MGH, higher numbers of ELN improved the overall survival for N0 patients. The prognostic significance (N0/N1) and PLN were too variable as the importance of a single PLN depended on the total number of LN dissected. LNR consistently correlated with survival once a certain number of lymph nodes were dissected (≥13 in SEER and ≥17 in the MGH dataset).
  
  
  CONCLUSIONS
  Better survival for N0 patients with increasing ELN likely represents improved staging. PLN have some predictive value but the ELN strongly influence their impact on survival, suggesting the need for a ratio-based classification. LNR strongly correlates with outcome provided that a certain number of lymph nodes is evaluated, suggesting that the prognostic accuracy of any LN variable depends on the total number of ELN.
authors.affiliation: Department of Surgery and Andrew L. Warshaw, M.D., Institute for Pancreatic Cancer Research, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
authors.forename: Nakul P
authors.initials: NP
authors.lastname: Valsangkar
authors.forename: Devon M
authors.initials: DM
authors.lastname: Bush
authors.forename: James S
authors.initials: JS
authors.lastname: Michaelson
authors.forename: Cristina R
authors.initials: CR
authors.lastname: Ferrone
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Wargo
authors.forename: Keith D
authors.initials: KD
authors.lastname: Lillemoe
authors.forename: Carlos
authors.initials: C
authors.lastname: Fernández-del Castillo
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Warshaw
authors.forename: Sarah P
authors.initials: SP
authors.lastname: Thayer
mesh_terms: D000368:Aged; D021441:Carcinoma, Pancreatic Ductal / Q000401:mortality* / Q000556:secondary*; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000401:mortality* / Q000473:pathology*; D011379:Prognosis; D015203:Reproducibility of Results; D016019:Survival Analysis; D015996:Survival Rate