title: Lymph node ratio may predict the benefit of postoperative radiotherapy in non-small-cell lung cancer.
abstract: BACKGROUND
  The use of postoperative radiotherapy (PORT) after resection of non-small-cell lung cancer (NSCLC) is controversial, with some evidence suggesting a benefit in patients with N2 disease. We assessed lymph node ratio (LNR) as a predictor of PORT benefit.
  
  
  METHODS
  By using the Surveillance, Epidemiology and End Results database, we analyzed resected, node-positive (N1-N2) NSCLC patients diagnosed between 1998 and 2009. LNR, (number of positive nodes/number of resected nodes) was categorized into four groups: LNR less than 12.5%, 12.5 to 24.9%, 25 to 49.9%, and 50% or more.
  
  
  RESULTS
  Of 11,324 node-positive NSCLC patients identified, 6551 (57.9%) had N1 disease. The LNR was prognostic for survival in the entire cohort and within each nodal stage. The median survival in LNR groups 1, 2, 3, and 4 was 43, 40, 30, and 23 months in N1 disease and 40, 32, 27, and 22 months in N2 disease, respectively. PORT was associated with a worse survival on univariate analysis (hazard ratio [HR] =1.09; confidence interval [CI] 1.03-1.15; p = 0.002) but no effect on multivariate analysis (HR = 0.96; CI 0.90-1.02; p = 0.201). When analyzed by nodal stage, the benefit of PORT was limited to N2 disease (HR = 0.9; CI 0.84-0.99; p= 0.026) with no benefit in N1 disease (HR = 1.06; CI 0.97-1.15; p=0.2). After stratifying by LNR, the survival benefit of PORT was limited to those with N2 disease and an LNR of 50% or more.
  
  
  CONCLUSIONS
  A high LNR is associated with a poorer survival in resected, node-positive NSCLC. The survival benefit associated with PORT in this disease seems to be limited to those with an LNR of 50% or more. This warrants further investigation in other cohorts and prospective studies.
authors.affiliation: Department of Medical Oncology, Peter MacCallum Cancer Centre, East Melbourne, Australia. damien.urban@petermac.org
authors.forename: Damien
authors.initials: D
authors.lastname: Urban
authors.forename: Jair
authors.initials: J
authors.lastname: Bar
authors.forename: Benjamin
authors.initials: B
authors.lastname: Solomon
authors.forename: David
authors.initials: D
authors.lastname: Ball
mesh_terms: D000230:Adenocarcinoma / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy; D002282:Adenocarcinoma, Bronchiolo-Alveolar / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy; D000368:Aged; D000369:Aged, 80 and over; D018287:Carcinoma, Large Cell / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy; D002289:Carcinoma, Non-Small-Cell Lung / Q000401:mortality* / Q000473:pathology / Q000532:radiotherapy; D002294:Carcinoma, Squamous Cell / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000401:mortality* / Q000473:pathology / Q000532:radiotherapy; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy; D009367:Neoplasm Staging; D011184:Postoperative Period; D011379:Prognosis; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D018426:SEER Program; D015996:Survival Rate