title: Association between lymph node evaluation for colon cancer and node positivity over the past 20 years.
abstract: BACKGROUND
  Among patients surgically treated for colon cancer, better survival has been demonstrated in those with more lymph nodes evaluated. The presumed mechanism behind this association suggests that a more extensive lymph node evaluation reduces the risk of understaging, leading to improved survival.
  
  
  OBJECTIVE
  To further evaluate the mechanism behind lymph node evaluation and survival by examining the association between more extensive lymph node evaluation, identification of lymph node-positive cancers, and hazard of death.
  
  
  METHODS
  Observational cohort study.
  
  
  METHODS
  Surveillance, Epidemiology, and End Results (SEER) program data from 1988 through 2008.
  
  
  METHODS
  86,394 patients surgically treated for colon cancer.
  
  
  METHODS
  We examined the relationship between lymph node evaluation and node positivity using Cochran-Armitage tests and multivariate logistic regression. The association between lymph node evaluation and hazard of death was evaluated using Cox proportional hazards modeling.
  
  
  RESULTS
  The number of lymph nodes evaluated increased from 1988 to 2008 but did not result in a significant overall increase in lymph node positivity. During 1988-1990, 34.6% of patients (3875/11,200) had 12 or more lymph nodes evaluated, increasing to 73.6% (9798/13,310) during 2006-2008 (P < .001); however, the proportion of node-positive cancers did not change with time (40% in 1988-1990, 42% in 2006-2008, P = .53). Although patients with high levels of lymph node evaluation were only slightly more likely to be node positive (adjusted odds ratio for 30-39 nodes vs 1-8 nodes, 1.11; 95% CI, 1.02-1.20), these patients experienced significantly lower hazard of death compared with those with fewer nodes evaluated (adjusted hazard ratio for 30-39 nodes vs 1-8 nodes, 0.66; 95% CI, 0.62-0.71; unadjusted 5-year mortality, 35.3%).
  
  
  CONCLUSIONS
  The number of lymph nodes evaluated for colon cancer has markedly increased in the past 2 decades but was not associated with an overall shift toward higher-staged cancers, questioning the upstaging mechanism as the primary basis for improved survival in patients with more lymph nodes evaluated.
authors.affiliation: Applied Research Program, National Cancer Institute, Executive Plaza North, 6130 Executive Blvd, MSC 7344, Bethesda, MD 20892-7344, USA. helen.parsons@nih.gov
authors.forename: Helen M
authors.initials: HM
authors.lastname: Parsons
authors.forename: Todd M
authors.initials: TM
authors.lastname: Tuttle
authors.forename: Karen M
authors.initials: KM
authors.lastname: Kuntz
authors.forename: James W
authors.initials: JW
authors.lastname: Begun
authors.forename: Patricia M
authors.initials: PM
authors.lastname: McGovern
authors.forename: Beth A
authors.initials: BA
authors.lastname: Virnig
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003110:Colonic Neoplasms / Q000401:mortality* / Q000473:pathology* / Q000601:surgery; D005260:Female; D006801:Humans; D008197:Lymph Node Excision; D008198:Lymph Nodes / Q000473:pathology; D008207:Lymphatic Metastasis / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods*; D017063:Outcome Assessment, Health Care; D018426:SEER Program; D016019:Survival Analysis