History of Smoking and Prognosis of Patients With Non-small Cell Lung Cancer

Background/Aim: Smoking is a known risk factor for the development of non-small-cell lung cancer (NSCLC). However, conflicting results are reported in the literature regarding the risk of smoking on the prognosis of patients with NSCLC. Moreover, these studies were often conducted before the era of personalized targeted therapy and immunotherapy, which can significantly improve the prognosis of patients. The aim of the present study was to evaluate the prognosis of patients with NSCLC in relation to their smoking history. Patients and Methods: This retrospective multicentre study included all patients from the Czech LUCAS registry with baseline tumour characteristics. Overall survival was assessed using Kaplan-Meier estimates, with differences between groups evaluated by the log-rank test and multivariate Cox regression model, adjusting for covariates and stratifying by disease stage when proportional hazards assumptions were violated. Results: A total of 3,372 patients were included. In the univariate model, non-smokers had a significantly better prognosis than former and current heavy smokers (with a history of ≥40 pack-years), hazard ratio=1.19 (95% confidence interval=1.01-1.42), p=0.043; and hazard ratio 1.19 (95% confidence interval=0.03-1.37), p=0.018, respectively. This relationship was not significant in the multivariate model. The absence of a prognostic significance of smoking at the time of NSCLC diagnosis was also demonstrated in a multivariate model both in patients with advanced disease treated with anticancer drugs and in patients who underwent surgery. Conclusion: Although smoking/ex-smoking at the time of NSCLC diagnosis had a negative prognostic impact in univariate analysis, multivariate analysis did not demonstrate smoking itself as an independent prognostic factor for NSCLC. Therefore, other factors, including poorer performance status, likely contributed to the poorer outcome for smokers.