title: T1aN0M0 and T1bN0M0 non-small cell lung cancer: a retrospective study of the prognosis.
abstract: BACKGROUND
  Stage IA of non-small cell lung cancer (NSCLC) is divided into two subgroups, T1aN0M0 (d ≤ 2 cm) and T1bN0M0 (2 < d ≤ 3 cm), in the International Association for the Study of Lung Cancer, seventh edition of TNM Classification of Malignant Tumors.
  
  
  OBJECTIVE
  The purpose of this study was the identification of independent clinicopathological predictors of prognosis of these two subgroups of NSCLC.
  
  
  METHODS
  Between 1986 and 2005, a cohort of 1,929 cases of stage IA NSCLC in Tian Jin Medical University Cancer Institute and Hospital were retrospectively analyzed. The impact of clinicopathological characteristics on patients' survival was investigated.
  
  
  RESULTS
  The overall 5-year survival rate was 71.07%. Patients with T1aN0M0 NSCLC had a better 5-year survival than those with T1bN0M0 (73.98 vs. 68.18%, p = 0.0135). The Cox proportional hazard model revealed that the prognostic factors of T1aN0M0 were intratumoral vessel invasion (p = 0.035) and histologic differentiation (p = 0.004). In patients with T1bN0M0 NSCLC, the prognostic factors were histologic differentiation (p < 0.01), intratumoral vessel invasion (p < 0.01), removal of 6 or more lymph node stations (p < 0.01), and removal of lymph node station 7 (p < 0.01).
  
  
  CONCLUSIONS
  Prognostic factors of T1aN0M0 and T1bN0M0 NSCLC are different. In patients with T1bN0M0 NSCLC, 6 or more lymph node stations and lymph node station 7 should be removed.
authors.affiliation: Department of Lung Cancer, Lung Cancer Center, Tian Jin Medical University Cancer Institute and Hospital, Tian Jin, People's Republic of China.
authors.forename: Zhenfa
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Lung Cancer, Lung Cancer Center, Tian Jin Medical University Cancer Institute and Hospital, Tian Jin, People's Republic of China.
authors.forename: Anlei
authors.initials: A
authors.lastname: Wang
authors.affiliation: Department of Pathology, Tian Jin Medical University Cancer Institute and Hospital, Tian Jin, People's Republic of China.
authors.forename: Zhongli
authors.initials: Z
authors.lastname: Zhan
authors.affiliation: Department of Pathology, Tian Jin Medical University Cancer Institute and Hospital, Tian Jin, People's Republic of China.
authors.forename: Leina
authors.initials: L
authors.lastname: Sun
authors.affiliation: Department of Epidemiology, Tian Jin Medical University Cancer Institute and Hospital, Tian Jin, People's Republic of China.
authors.forename: Kexin
authors.initials: K
authors.lastname: Chen
authors.affiliation: Department of Lung Cancer, Lung Cancer Center, Tian Jin Medical University Cancer Institute and Hospital, Tian Jin, People's Republic of China.
authors.forename: Changli
authors.initials: C
authors.lastname: Wang
mesh_terms: D001706:Biopsy; D002289:Carcinoma, Non-Small-Cell Lung / Q000401:mortality / Q000473:pathology* / Q000601:surgery; D002681:China / Q000453:epidemiology; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000401:mortality / Q000473:pathology* / Q000601:surgery; D008297:Male; D008481:Mediastinoscopy; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D011013:Pneumonectomy; D049268:Positron-Emission Tomography; D011379:Prognosis; D012189:Retrospective Studies; D015996:Survival Rate / Q000639:trends; D013997:Time Factors; D014057:Tomography, X-Ray Computed