title: Stage migration effect on survival in gastric cancer surgery with extended lymphadenectomy: the reappraisal of positive lymph node ratio as a proper N-staging.
abstract: OBJECTIVE
  The purpose of this study is to analyze the relationship between the number of examined lymph nodes (NexLN) and survival in gastric cancer and to determine whether the metastatic/examined lymph node ratio (LN ratio) system can compensate for the shortcomings of the UICC/AJCC staging.
  
  
  METHODS
  Prospective data of 8949 primary T1-T4a gastric cancer patients who underwent curative surgery were reviewed. The patients were stratified by T-stage and grouped according to NexLN; 1 to 14 exLN denoted the first group and every subsequent 10 LNs thereafter. Numbers of LN and 5-year survival rates were analyzed according to NexLN. "The NR-staging system" was generated using 0.2 and 0.5 as the cut-off values of LN ratio and then compared with UICC/AJCC stages.
  
  
  RESULTS
  The proportion of advanced N-stage increased with NexLN. Survival and the LN ratio were constant regardless of NexLN when combining all N0-N3b patients, however, T2/3 and T4a patients showed an increasing tendency toward survival in N1/2 and N3a as NexLN increased, mainly due to a stage migration effect. The LN ratio system showed better patterns of distribution of the LN stage and survival graph. The power of the differential staging of the LN ratio system was fortified with higher NexLN.
  
  
  CONCLUSIONS
  The relationship between NexLN and survival is probably affected by stage migration in a high-volume gastric cancer center. The LN ratio system could be a better option to compensate for this effect, and the value of the prognosis prediction in this system increases with a higher NexLN.
authors.affiliation: Department of Surgery, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Seong-Ho
authors.initials: SH
authors.lastname: Kong
authors.forename: Hyuk-Joon
authors.initials: HJ
authors.lastname: Lee
authors.forename: Hye Seong
authors.initials: HS
authors.lastname: Ahn
authors.forename: Jong-Won
authors.initials: JW
authors.lastname: Kim
authors.forename: Woo Ho
authors.initials: WH
authors.lastname: Kim
authors.forename: Kuhn Uk
authors.initials: KU
authors.lastname: Lee
authors.forename: Han-Kwang
authors.initials: HK
authors.lastname: Yang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002173:Cancer Care Facilities; D018450:Disease Progression; D005260:Female; D005743:Gastrectomy / Q000401:mortality; D006801:Humans; D008197:Lymph Node Excision / Q000379:methods* / Q000401:mortality; D008198:Lymph Nodes / Q000473:pathology; D008207:Lymphatic Metastasis / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D013223:Statistics as Topic; D013274:Stomach Neoplasms / Q000401:mortality / Q000473:pathology* / Q000601:surgery*; D015996:Survival Rate