title: The influence of smoking intensity on the clinicopathologic features and survival of patients with surgically treated non-small cell lung cancer.
abstract: BACKGROUND
  Smoking is a well-known carcinogen for lung cancer. However, whether smoking affects the biological behavior of lung cancer remains uncertain. This study aimed to investigate the influences of smoking intensity on the clinicopathologic characteristics of and survival in non-small cell lung cancer (NSCLC).
  
  
  METHODS
  We retrospectively reviewed 2238 consecutive patients who underwent surgical resection for NSCLC between 1990 and 2010. Smoking intensity was defined as pack-years (PY). The patients were divided into three groups according to the median value of smoking intensity (40 PY): group A (never smokers), group B (smoking intensity less than 40 PY) and group C (smoking intensity more than 40 PY).
  
  
  RESULTS
  There were 1629 (72.8%) male patients, and the mean age was 61.71 ± 13.17 years. Adenocarcinoma was reported in 1058 (47.3%) patients. The median follow-up period was 30.7 months (range: 0.0-261.7 months). The 5-year overall survivals for groups A, B and C were 60.1%, 51.6% and 43.2%, respectively (p < 0.001). In subset analysis by histology, the 5-year overall survival was significantly different according to smoking intensity in adenocarcinoma (p < 0.001), but there was no difference in the non-adenocarcinoma. In adenocarcinoma, the incidences of vascular invasion (p = 0.028), pleural invasion (p = 0.013) and poor differentiation (p < 0.001) were higher and tumor sizes (p < 0.001) were greater in group C than others. On multivariate analysis, smoking intensity was an adverse risk factor for overall survival in surgically treated adenocarcinoma patients (hazard ratio = 1.008, p = 0.028).
  
  
  CONCLUSIONS
  Smoking intensity was an adverse prognostic factor after surgical resection of adenocarcinoma. Heavy smoking was correlated with poor pathologic characteristics in adenocarcinoma.
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Yonsei University, College of Medicine, Seoul, Republic of Korea.
authors.forename: Seong Yong
authors.initials: SY
authors.lastname: Park
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Yonsei University, College of Medicine, Seoul, Republic of Korea.
authors.forename: Jin Gu
authors.initials: JG
authors.lastname: Lee
authors.affiliation: Biostatistics Collaboration Unit, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Jieun
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Yonsei University, College of Medicine, Seoul, Republic of Korea.
authors.forename: Mi Kyung
authors.initials: MK
authors.lastname: Bae
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Yonsei University, College of Medicine, Seoul, Republic of Korea.
authors.forename: Chang Young
authors.initials: CY
authors.lastname: Lee
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Yonsei University, College of Medicine, Seoul, Republic of Korea.
authors.forename: Dae Joon
authors.initials: DJ
authors.lastname: Kim
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Yonsei University, College of Medicine, Seoul, Republic of Korea. Electronic address: kychu@yuhs.ac.
authors.forename: Kyung Young
authors.initials: KY
authors.lastname: Chung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000453:epidemiology* / Q000209:etiology* / Q000601:surgery; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000453:epidemiology* / Q000209:etiology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D012189:Retrospective Studies; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D016019:Survival Analysis
keywords: Lung cancer surgery; Smoking; Statistics; Survival analysis