The association between smoking abstinence and mortality in the national lung screening trial

Rationale: Smoking is the largest contributor to lung cancer risk, and those who continue to smoke after diagnosis have a worse survival. Screening for lung cancer with low-dose computed tomography (LDCT) reduces mortality in high-risk individuals. Smoking cessation is an essential component of a high-quality screening program. Objectives: To quantify the effects of smoking history and abstinence on mortality in high-risk individuals who participated in the NLST (National Lung Screening Trial). Methods: This is a secondary analysis of a randomized controlled trial (NLST). Measurements and Main Results: Measurements included self-reported demographics, medical and smoking history, and lung cancer-specific and all-cause mortality. Cox regression was used to study the association of mortality with smoking status and pack-years. Kaplan-Meier survival curves were examined for differences in survival based on trial arm and smoking status. Current smokers had an increased lung cancer-specific (hazard ratio [HR], 2.14-2.29) and all-cause mortality (HR, 1.79-1.85) compared with former smokers irrespective of screening arm. Former smokers in the control arm abstinent for 7 years had a 20% mortality reduction comparable with the benefit reported with LDCT screening in the NLST. The maximum benefit was seen with the combination of smoking abstinence at 15 years and LDCT screening, which resulted in a 38% reduction in lung cancer-specific mortality (HR, 0.62; 95% confidence interval, 0.51-0.76). Conclusions: Seven years of smoking abstinence reduced lung cancer-specific mortality at a magnitude comparable with LDCT screening. This reduction was greater when abstinence was combined with screening, highlighting the importance of smoking cessation efforts in screening programs.