title: The number of lymph nodes dissected in breast cancer patients influences the accuracy of prognosis.
abstract: BACKGROUND
  Recent trials have suggested that axillary node dissection may not be warranted in some breast cancer patients with one to two positive nodes. Given that lymph node ratio (LNR; number of positive lymph nodes divided by the total examined) has been shown to be a significant prognostic factor, we sought to determine whether the number of nodes removed in this low risk population predicted survival.
  
  
  METHODS
  The National Cancer Database is a comprehensive clinical surveillance resource capturing 70% of newly diagnosed malignancies in the United States; 309,216 breast cancer patients diagnosed between 1998 and 2005, with tumors ≤5 cm and one to two positive nodes, formed the cohort of interest.
  
  
  RESULTS
  Median age at diagnosis was 57 (range 18-90) years. Median tumor size was 2 (range 0.1-5) cm; 215,382 patients (69.7%) had one positive node, and 93,834 (30.3%) had two. The median number of lymph nodes examined was 11 (range 1-84). Patients were categorized into low (≤0.2), medium (0.21-0.65), or high (>0.65) LNR groups, with 228,822 (74%), 55,797 (18%), and 24,597 (8%) patients in each of these categories, respectively. Median follow-up was 54.1 months. Median overall survival (OS) for low, intermediate, and high LNR was 66.1, 61.1, and 56.5 months, respectively (p < 0.001). In a Cox model controlling for clinicopathologic and therapy covariates, LNR category remained a significant predictor of OS (p < 0.001).
  
  
  CONCLUSIONS
  LNR is an independent predictor of OS in a low-risk population with one to two positive nodes and tumors ≤5 cm. Therefore, the number of lymph nodes excised may influence prognostic stratification.
authors.affiliation: Department of Surgery, Yale University School of Medicine, New Haven, CT, USA, lauren.wiznia@yale.edu.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Wiznia
authors.forename: Donald R
authors.initials: DR
authors.lastname: Lannin
authors.forename: Suzanne B
authors.initials: SB
authors.lastname: Evans
authors.forename: Erin W
authors.initials: EW
authors.lastname: Hofstatter
authors.forename: Nina R
authors.initials: NR
authors.lastname: Horowitz
authors.forename: Brigid K
authors.initials: BK
authors.lastname: Killelea
authors.forename: Theodore N
authors.initials: TN
authors.lastname: Tsangaris
authors.forename: Anees B
authors.initials: AB
authors.lastname: Chagpar
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000401:mortality* / Q000473:pathology / Q000601:surgery*; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008197:Lymph Node Excision / Q000401:mortality*; D008198:Lymph Nodes / Q000473:pathology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D015996:Survival Rate; D055815:Young Adult