title: Lymph Node Ratio Is Less Prognostic in Melanoma When Minimum Node Retrieval Thresholds Are Not Met.
abstract: BACKGROUND
  Lymph node ratio (LNR), positive nodes divided by nodes examined, has been proposed for prognostication in melanoma to mitigate problems with low node counts. However, it is unclear if LNR offers superior prognostication over total counts of positive nodes and nodes examined. Additionally, the prognostic value of LNR may change if a threshold number of nodes are examined. We evaluated whether LNR is more prognostic than positive nodes and nodes examined, and whether the prognostic value of LNR changes with minimum thresholds.
  
  
  METHODS
  Using the National Cancer Data Base Participant User File, we identified 74,692 incident cases with nodal dissection during 2000-2006. We compared LNR versus counts of examined and positive nodes based on Harrell's C, a measure of predictive ability. We then stratified by total nodes examined: greater versus fewer than ten for axillary lymph node dissection (ALND) and greater versus fewer than five for inguinal lymph node dissection (ILND).
  
  
  RESULTS
  Overall, LNR had a Harrell's C of 0.628 (95 % confidence interval [CI] 0.625-0.631). Examined and positive nodes were not significantly different from this, with a Harrell's C of 0.625 (95 % CI 0.621-0.630). In ALND, LNR had a Harrell's C of 0.626 (95 % CI 0.610-0.643) with ≥10 nodes versus 0.554 (95 % CI 0.551-0.558) < 10 nodes. In ILND, LNR had a Harrell's C of 0.679 (95 % CI 0.664-0.694) with ≥5 nodes versus C of 0.601 (95 % CI 0.595-0.606) < 5 nodes.
  
  
  CONCLUSIONS
  LNR provides no prognostic superiority versus counts of examined and positive nodes. Moreover, the prognostic value of LNR diminishes when minimum node retrieval thresholds are not met.
authors: Department of Surgery, University of Michigan, Ann Arbor, MI, USA. healym@umich.edu.|Center for Healthcare Outcomes and Policy, University of Michigan, Ann Arbor, MI, USA. healym@umich.edu.
authors: Mark A
authors: MA
authors: Healy
authors: Center for Healthcare Outcomes and Policy, University of Michigan, Ann Arbor, MI, USA.|Department of Biostatistics, University of Michigan, Ann Arbor, MI, USA.
authors: Evan
authors: E
authors: Reynolds
authors: Center for Healthcare Outcomes and Policy, University of Michigan, Ann Arbor, MI, USA.|Department of Biostatistics, University of Michigan, Ann Arbor, MI, USA.
authors: Mousumi
authors: M
authors: Banerjee
authors: Department of Surgery, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA.
authors: Sandra L
authors: SL
authors: Wong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008197:Lymph Node Excision / Q000401:mortality*; D008198:Lymph Nodes / Q000473:pathology* / Q000601:surgery; D008297:Male; D008545:Melanoma / Q000401:mortality / Q000473:pathology / Q000601:surgery*; D008875:Middle Aged; D015233:Models, Statistical; D011379:Prognosis; D015996:Survival Rate