Incidence and mortality trends after introduction of lung cancer screening in a community-based healthcare system

BACKGROUND: Lung cancer screening (LCS) enables early cancer detection but raises concerns about overdiagnosis, particularly in community-based LCS settings where evidence remains limited. This study examined trends in lung cancer incidence and mortality following the introduction of LCS in a community-based setting and used these trends to assess the potential of LCS-associated overdiagnosis. METHODS: This retrospective study leveraged data and outcomes from the Kaiser Permanente Colorado (KPCO) LCS program between 2014 and 2023. Trends in lung cancer incidence and mortality were assessed by annual percent change (APC). Excess incidence was estimated by comparing post-LCS early-stage lung cancer incidence with pre-LCS program implementation and predicted incidence and expressed as counts and percentage of lung cancers. RESULTS: Among 1006 incident lung cancers, 619 (62%) were early stage, 367 (37%) were late stage, and 20 (2%) had unknown stage; 198 lung cancer deaths were identified. Early-stage incidence increased (APC, 4.9%; 95% confidence interval (CI), -1.6-1.8%), late-stage incidence decreased (APC, -5.2%; 95% CI, -9.8% to -0.3%) and mortality decreased (APC, -6.0%, 95% CI, -12.3-0.8). Excess incidence suggests that 11.3%-35.9% of early-stage lung cancer cases could represent potential overdiagnosis, with only a portion of these reflecting true overdiagnosis. CONCLUSION: We observed patterns consistent with a maturing LCS screening program including a non-significant increase in early-stage detection, significant reduction in late-stage disease, and a non-significant decline in lung cancer-specific mortality. These findings provide an important starting point for understanding the impact of LCS on the distribution of stage in community-based screening programs. Continued monitoring of lung cancer incidence and mortality remains essential to refine estimates and evaluate their implications for healthcare resources, survivorship care, and the net benefit of screening.