Influence of cigarette smoking on survival and tumor invasiveness in clinical stage IA lung adenocarcinoma

Background: The objective of this study was to investigate the association between cigarette smoking, cancer survival, and pathological features of clinical stage IA lung adenocarcinoma. Methods: Between August 1992 and December 2007, 1,070 consecutive patients with clinical stage IA lung adenocarcinoma underwent complete resection with systematic lymph node dissection. Univariate analysis by log-rank tests was performed to determine unfavorable prognostic factors, and the Cox proportional hazards regression model was used to identify the potential independent predictors. Results: The overall 5-year survival rate of patients with greater than 20 pack-years (PY > 20) was 71%, significantly lower than patients with 20 or less pack-years (PY ≤ 20; 86%; p < 0.001). Postoperative pathological prognostic factors, including moderate or poor histologic differentiation, lymphatic permeation, intratumoral vascular invasion, visceral pleural invasion, and lymph node metastasis, were detected more often in patients with greater than 20 PY. Sixty-five percent of the patients in this study had pathological stage IA tumors, and their overall 5-year survival rates with 20 or less PY and greater than 20 PY were 97% and 86%, respectively (p < 0.001). Conclusions: In patients with clinical stage IA adenocarcinoma, a history of heavy smoking was associated with poor outcomes and was a statistically significant predictor of histologic tumor invasion.