title: Classifications of n2 non-small-cell lung cancer based on the number and rate of metastatic mediastinal lymph nodes.
abstract: BACKGROUND
  Subdivisions of N2 non-small-cell lung cancer (NSCLC) cases based on metastatic status of mediastinal and non-mediastinal lymph nodes have been proposed. This study aimed to evaluate N2 disease classification by mediastinal lymph nodes alone.
  
  
  METHODS
  We reviewed 187 patients with NSCLC pN1-N2 who were surgically treated to evaluate the proposed classifications: number, rate, nodal zone of metastatic lymph nodes. We evaluated N2 disease classification based on mediastinal lymph nodes alone in 136 pN2 cases.
  
  
  RESULTS
  The number (1-2, 3-5, and 6 ≤) or rate (15%≥, 15%< to 40%>, and 40%≤) classification based on all metastatic lymph nodes was validated by the log-rank test and Cox proportional hazards model. After reclassification by number or rate of metastatic mediastinal lymph nodes alone, a significant difference was maintained among all groups except between the 3-5 and 6 ≤ groups. The 5-year survival rates of the 1-2, 3-5, and 6 ≤ groups were 63.4%, 32.4%, and 18.2%, respectively (1-2 vs. 3-5, P = .015; 3-5 vs. 6 ≤, P = .134). With rate classification, the 5-year survival rates of the 15%≥, 15%-40% (15%< to 40%>), and 40%≤ groups were 56.0%, 27.3%, and 5.04%, respectively (15%≥ vs. 15%-40%, P = .011; 15-40% vs. 40%≤, P = .011). The Spearman's rank correlation coefficient showed a highly significant correlation of metastatic status between mediastinal lymph nodes and all lymph nodes (both P < .001).
  
  
  CONCLUSIONS
  Classification by number and rate of mediastinal lymph nodes alone enabled subdivision of N2 NSCLC cases. Metastatic status of mediastinal lymph nodes reflects that of all lymph nodes and is prognostic indicators.
authors.affiliation: Department of General Thoracic Surgery, National Hospital Organization Kure Medical Center and Chugoku Cancer Center, Kure; Department of Surgical Oncology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan.
authors.forename: Masaoki
authors.initials: M
authors.lastname: Ito
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Tsutani
authors.forename: Keizo
authors.initials: K
authors.lastname: Misumi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Harada
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Miyata
authors.forename: Morihito
authors.initials: M
authors.lastname: Okada
mesh_terms: D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000145:classification / Q000175:diagnosis* / Q000401:mortality; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000145:classification / Q000175:diagnosis* / Q000401:mortality; D008198:Lymph Nodes / Q000473:pathology* / Q000601:surgery; D008207:Lymphatic Metastasis / Q000473:pathology*; D008297:Male; D008482:Mediastinum / Q000473:pathology*; D009367:Neoplasm Staging; D011379:Prognosis; D016016:Proportional Hazards Models; D016019:Survival Analysis; D016896:Treatment Outcome
keywords: Lymph node; N2 disease; Non–small-cell lung cancer; Prognosis; Tumor staging