Screening-Detected Versus Interval Lung Cancer in the Biennial Korean National Lung Cancer Screening Program: Proportion, Characteristics, and Mortality

Introduction: Interval lung cancers (ILCs) are key indicators of lung cancer screening (LCS) performance. However, data on the proportion, characteristics, and mortality of ILCs under biennial screening in Asian populations remain limited. Methods: We analyzed participants from the baseline biennial Korean national LCS program between 2019 and 2020. Screening-detected lung cancers (SLCs) were defined as those diagnosed within 1 year of a positive screening result. ILCs were defined as cancers diagnosed more than 1 year after a negative screening result but within 2 years or before the next screening. Risk factors for ILC were assessed using multivariable logistic regression among participants with a negative screening result. All-cause mortality was compared between SLCs and ILCs using multivariable Cox regression analysis. Results: Among 124,595 participants, SLCs and ILCs occurred in 0.56% and 0.17%, respectively. ILCs accounted for 18.5% of all lung cancers within 2 years; 65.4% were in Lung-RADS category 1. Risk factors for ILC included older age (adjusted odds ratio [OR], 1.14; 95% confidence interval [CI]: 1.11–1.17; p < 0.001), greater smoking exposure (adjusted OR, 1.010; 95% CI: 1.004–1.016; p = 0.002), a history of malignancy (adjusted OR, 2.22; 95% CI: 1.41–3.51; p < 0.001), emphysema (adjusted OR, 2.88; 95% CI: 2.15–3.85; p < 0.001), and interstitial lung abnormalities (adjusted OR, 4.16; 95% CI: 2.88–6.01; p < 0.001). ILCs had higher all-cause mortality than SLCs (adjusted hazard ratio, 1.43; 95% CI: 1.13–1.80; p = 0.002). Conclusions: ILCs are common under biennial LCS, making them potentially suboptimal for Asian heavy smokers.