Background: Previous studies have attempted to investigate the impact of smoking cessation on lung cancer survival but have been limited by small numbers of former smokers and incomplete data.
Methods: Over a six-year period, 5229 patients with non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC) were enrolled in a prospective cohort of whom 2052 were former smokers. Patient's characteristics were obtained from medical records and a baseline interview. Vital status was determined through multiple sources. Cox proportional hazards models were used to estimate the effect of smoking abstinence on post-diagnosis mortality.
Results: For all patients with NSCLC, the median survival among never, former, and current smokers was 1.4 years, 1.3 years, and 1.1 years, respectively (P < 0.01). Female NSCLC patients had a significantly lower risk of mortality with a longer duration of smoking abstinence (RR per 10 years of smoking abstinence = 0.85; 95% CI: 0.75, 0.97). No effect of smoking abstinence on mortality was observed for women with SCLC or for men with either histologic group.
Conclusions: The identification of smoking history as a prognostic factor in lung cancer survival supports previous research suggesting a direct biologic effect of smoking on survival. However, this effect may vary by sex and type of lung cancer.