The prognostic impact of the amount of tobacco smoking in non-small cell lung cancer-Differences between adenocarcinoma and squamous cell carcinoma

Backgrounds: The purpose of this study was to investigate the relationship between the level of tobacco smoking and the clinicopathological features of non-small cell lung cancer (NSCLC) patients, individually for adenocarcinoma (Ad) and squamous cell carcinoma (Sq). Patients and methods: We retrospectively reviewed the clinical records of 1825 consecutive lung cancer patients who underwent surgery in our department. Among these, the data sets of 750 Ad patients and 364 Sq patients who received lobectomy or more extensive resection were available. Results: In Ad patients, those who had never smoked (never-smokers) (n= 309) were more likely to be female, to have less advanced stage tumors, and to have a significantly better prognosis than those who had ever smoked (ever-smokers) (n= 441) (5-year OS: never-smokers, 67.9%; ever-smokers, 53.7%, p< 0.0001). In Sq patients, the never-smokers (n= 15) were more likely to be female than the ever-smokers (n= 349). Among ever-smokers, the light-smokers (PY ≤ 30; n= 56) were associated with more female patients, more advanced stage tumors, and significantly worse prognoses than were the heavy smokers (PY > 30; n= 292) (p= 0.0003). The multivariate survival analysis showed that light smoking was related to a worse prognosis compared with heavy smoking (HR = 2.06, 95% CI 1.43-2.98, p= 0.0001). Conclusions: The never-smokers had a significantly better prognosis than ever-smokers among Ad patients, whereas the light-smokers had a significantly worse prognosis than heavy smokers among Sq patients. There may be factors other than tobacco carcinogens that influence the development of Sq in never and/or light smokers.