Diagnostic Performance of the Modified Lung-RADS in a Tuberculosis-endemic Country: The Korean National Lung Cancer Screening Program.

Background: In 2019, Korea initiated the world's first national low-dose computed tomography (CT) lung cancer screening (LCS) program, adapting the Lung CT Screening Reporting and Data System (Lung-RADS) to counteract the high false-positive rates driven by prevalent tuberculosis.

Research Question: Does the modified Lung-RADS enhance screening specificity while maintaining sensitivity?

Study Design And Methods: This nationwide, retrospective, cohort study included high-risk current smokers aged 54 to 74 with at least 30 pack-years, participating in the national LCS program from 2019 to 2020. The modified Lung-RADS 1.0 introduced category 2b for nodules matching the size of categories 3 or 4 but showing benign features like granulomas and juxtapleural nodules, and enhanced details for category 4X. Lung cancer diagnosis rates within a year of screening and the diagnostic performance of the modified and original Lung-RADS were evaluated.

Results: Among 152,918 participants (98.2% male; mean age, 61.7±5.3 years), lung cancer was diagnosed in 0.68% (1,047/152,918). There was a linear trend in cancer rates across Lung-RADS categories (P<0.001). Category 2b showed a higher cancer rate than category 2 (0.25% [45/18,120] vs. 0.14% [33/23,467]; P=0.01) but lower than category 3 (0.53% [37/7,009]; P=0.001). Category 4X had a cancer rate of 36.88% (416/1,128). The modified Lung-RADS demonstrated improved specificity (91.96% [139,664/151,871] vs. 80.06% [121,589/151,871]; P<0.001) compared to the original criteria. While sensitivity showed a modest decrease (81.9% [858/1,047] vs. 86.2% [903/1,047]; P<0.001), the modification substantially reduced the follow-up burden, decreasing the number of positive screenings needed to detect one cancer from 34.5 to 15.2. The positive predictive value improved significantly (2.90% [903/31,185] to 6.57% [858/13,065]; P<0.001), while the negative predictive value remained consistently high (modified: 99.86% [139,664/139,853] vs. original: 99.88% [121,589/121,733]; P=0.23).

Interpretation: Korea's modified Lung-RADS enhanced screening efficiency through improved specificity despite a small reduction in sensitivity.

Clinical Trial Registration: N/A.