Smoking Cause Specific Lung Cancer—Evidence from Non-Smoking Lung Adenocarcinoma

Abstract

Introduction: Smoking and non-smoking lung cancer have many differences in clinical feature. But those may be the result of interference due to differences in pathological type, as most smoking patients suffer squmous cell lung cancer and non-smokings tend to get adenocarcinoma. This study was conducted on the specific histological type-lung adenocarcinoma-to avoid histological bias and to reveal the true effect of smoking. Methods: A total of 2222 patients with lung adenocarcinoma confirmed by histological or cytological evidence were enrolled from January 1, 1999 to December 31, 2004. Differences in clinical features and prognosis between non-smoking and smoking patients were analyzed.Chisquare test was used for univariate comparisons. Univariate probability of survival was computed using Kaplan-Meier estimate and compared to using the log-rank test. Cox proportional hazards regression analysis was used to evaluate the risk of death. Results: There were 777 current smokers (34.96%), 197 former smokers (8.87%) and 1248 non-smoking patients (56.17%). 860 non-smoking patients (68.91%) were female, compared with 6.31% among current smokers and 4.06% among former smokers (p < 0.001). Non-smoking patients had an earlier age at diagnosis (p < 0.001) and a better response to chemotherapy (p < 0.001) compared to current smoking patients. Current smoking correlated with lower cell differentiation (p < 0.001) and worse prognosis (p = 0.0024). After multivariate analysis, smoking was identified as an independent negative prognostic factor (HR, 1.302; 95% CI, 1.011 - 1.6780, p = 0.041). No difference in prognosis was observed according to smoking conditions in smoking patients. Conclusions: Significent differences exist in clinical features and prognosis between non-smoking and smoking lung adenocarcinoma patients. There is a strong evidence that non-smoking lung adenocarcinoma should be regard as different disease.