Trends in lung cancer incidence and mortality and the potential for overdiagnosis associated with computed tomography screening across 21 countries on six continents.

Background: Lung cancer remains a leading cause of cancer-related deaths worldwide. While low-dose computed tomography (LDCT) screening has proven effective in reducing deaths among high-risk populations, its extension to average-risk individuals raises concern of potential overdiagnosis. Recent evidence from Shanghai, China, indicates this risk. However, cross-national ecological assessments remain limited. This study was therefore conducted to investigate population-level signals of potential lung cancer overdiagnosis across multiple countries. Methods: Using the Global Burden of Disease 2021 database, we analyzed temporal trends in lung cancer incidence and mortality across 21 countries selected for their large populations and disproportionate disease burden, including the United States, China, India, and Brazil. Potential overdiagnosis was assessed both qualitatively and quantitatively. Qualitatively, we inspected three decades of data and regarded a persistent rise in incidence alongside stable or declining mortality as an initial ecological signal of possible overdiagnosis. Quantitatively, we fitted an age-specific log-linear incidence model to historical data, projected model-expected incidence, and estimated the potential overdiagnosis rate as the excess of observed over expected cases. Results: Across most selected countries, lung cancer incidence and mortality changed broadly in parallel, providing limited evidence of overdiagnosis. China was the exception: after 2015, incidence increased while mortality declined. Quantitative analysis showed that the overdiagnosis rate among Chinese women was 2.71% between 2018 and 2021, with cases concentrated among those aged 60-75 years. No corresponding excess was observed in Chinese men. Conclusions: Population-level signals of potential lung cancer overdiagnosis were not uniformly observed across the selected countries. However, population-level trends in China suggest the possibility of excess detection among older women in recent years, most likely driven by non-targeted LDCT screening. These findings underscore the need for risk-stratified screening protocols and refined pulmonary nodule management to preserve the mortality benefits of early detection while minimizing the harms of overdiagnosis.