Clinical Outcomes of Interstitial Lung Abnormalities Detected in the Korean National Lung Cancer CT Screening Program

Background: Limited evidence exists on the prevalence and outcomes of interstitial lung abnormalities (ILAs) in lung cancer screening populations, particularly Asian populations. Purpose: To investigate the prevalence of ILAs and the association of ILAs with lung cancer, idiopathic pulmonary fibrosis (IPF), and mortality outcomes in an Asian population. Materials and Methods: In this nationwide, population-based retrospective study, baseline screenings from the Korean National Lung Cancer Screening Program performed between August 2019 and December 2020 were analyzed. ILAs were identified from CT structured reports based on program radiologists’ visual assessment, and ILA prevalence was analyzed across age groups. Incidence rate ratios were calculated for lung cancer incidence, IPF, and all-cause mortality comparing individuals with ILAs versus individuals without ILAs, and multivariable Cox regression analyses were performed to examine associations between ILAs and these outcomes. Results: Among 125 600 individuals (mean age, 62 years ± 5.3 [SD]; 123 331 men), ILA prevalence was 2.65% (3324 of 125 600) and was strongly associated with older age (P < .001). The lung cancer incidence rate was higher in the ILA group (2009 vs 412 per 100 000 person-years, P < .001; incidence rate ratio, 4.88), as was the all-cause mortality rate (2334 vs 712 per 100 000 person-years, P < .001; incidence rate ratio, 3.28). During a median follow-up of 2.9 years, IPF was diagnosed in 3.55% (118 of 3324) of individuals with ILAs (incidence rate, 1344 per 100 000 person-years in group with ILAs vs 18 per 100 000 person-years in group without ILAs, P < .001; incidence rate ratio, 73.24). In multivariable analyses, individuals with ILAs had a threefold higher risk of lung cancer (adjusted hazard ratio, 3.18 [95% CI: 2.71, 3.73]; P < .001) and twofold higher all-cause mortality (adjusted hazard ratio, 2.37 [95% CI: 2.09, 2.69]; P < .001). Individuals with ILAs showed a markedly higher risk of IPF diagnosis, with more than 60-fold higher risk (adjusted hazard ratio, 63.4 [95% CI: 45.9, 87.7]; P < .001). Conclusion: The presence of ILAs was associated with higher risks of lung cancer, IPF, and mortality.