Lung Cancer Screening with Low-Dose CT in Female Never Smokers: Retrospective Cohort Study with Long-term National Data Follow-up

PURPOSE: Because of growing concerns about lung cancer in female never smokers, chest low-dose computed tomography (LDCT) screening is often performed although it has never shown clinical benefits. We examinewhether or not female never smokers really need annual LDCT screening when the initial LDCT showed negative findings. MATERIALS AND METHODS: This retrospective cohort study included 4,365 female never smokers aged 40 to 79 years who performed initial LDCT from Aug 2002 to Dec 2007. Lung cancer diagnosis was identified from the Korea Central Cancer Registry Database registered until December 31, 2013. We calculated the incidence, cumulative probability, and standardized incidence ratio (SIR) of lung cancer by Lung Imaging Reporting and Data System (Lung-RADS) categories showed on initial LDCT. RESULTS: After median follow-up of 9.69 years, 22 (0.5%) had lung cancer. Lung cancer incidence for Lung-RADS category 4 was 1,848.4 (95% confidence interval [CI], 1,132.4 to 3,017.2) per 100,000 person-years and 16.4 (95% CI, 7.4 to 36.4) for categories 1, 2, and 3 combined. The cumulative probability of lung cancer for category 4 was 10.6% at 5 years and 14.8% at 10 years while they were 0.07% and 0.17% when categories 1, 2, and 3 were combined. The SIR for subjects with category 4 was 43.80 (95% CI, 25.03 to 71.14), which was much higher than 0.47 (95% CI, 0.17 to 1.02) for categories 1, 2, and 3 combined. CONCLUSION: Considering the low risk of lung cancer development in female never smokers, it seems unnecessary to repeat annual LDCT screening for at least 5 years or even longer unless the initial LDCT showed Lung-RADS category 4 findings.