Redefining lung cancer screening eligibility: Smoking duration vs. pack-years in a national VA cohort of nearly 1 million patients.

Abstract

8004 Background: Lung cancer is the leading cause of cancer death in the US, yet current lung cancer screening (LCS) criteria based on tobacco pack-years (TPY) miss nearly half of all cases and are difficult to capture reliably in clinical practice. Tobacco smoking duration (TSD) is a simpler, more consistently measurable metric that may better identify high-risk individuals. We evaluated whether TSD improves lung cancer risk prediction compared with TPY in a unique real-world cohort of nearly 1 million patients. Methods: We conducted a retrospective cohort study of Veterans aged 50–80 in the Veterans Health Administration. The primary exposure was smoking history quantified as TPY and TSD; the primary outcome was 5-year lung cancer incidence (2021-2025). We compared risk-adjusted 5-year lung cancer incidence based on 2013 USPSTF guidelines (≥30 TPY, quit within 15 years), revised 2021 USPSTF guidelines (≥20 TPY, quit within 15 years), our proposed TSD criteria (≥20 TSD), and never-smoking. We further estimated the impact of switching to TSD-based eligibility on the theoretical number of missed lung cancer diagnoses (i.e., the proportion of lung cancers diagnosed in screening-ineligible individuals) and performed subgroup analyses across race and sex. Results: A total of 960,770 Veterans were included in the study, with 340,312 (35.4%) currently smoking, 304,589 (31.7%) formerly smoking, and 315,869 (32.9%) never smoking. The median (SD) age was 64.9 (9.6) years old. Most participants were male (n=876,215, 91.2%) and of white race (n=677,823, 70.6%). 341,061 (35.5%) qualified for 2013 TPY criteria, 437,803 (45.6%) qualified for 2021 TPY criteria, and 571,087 (59.4%) qualified for TSD criteria. Importantly, 127,604 (22.3%) individuals who met TSD criteria did not meet 2021 TPY criteria, suggesting that TSD criteria would increase the eligible screening population by 28.8%. The 5-year incidence of lung cancer was 0.95% (1.87% among 2013 TPY criteria; 1.73% among 2021 TPY criteria; 1.48% among TSD criteria; and 0.13% among never-smoking). The proportion of missed lung cancer diagnoses was 30.3% among 2013 TPY criteria, 17.1% among 2021 TPY criteria, and 7.5% among TSD criteria. Finally, eligibility was higher for TSD vs. TPY criteria in various subgroups, including among black individuals (percent of current or former smokers eligible for screening: 34.7% 2013 TPY; 54.0% 2021 TPY; and 83.7% TSD) and females (38.5% 2013 TPY; 55.1% 2021 TPY; and 83.7% TSD). Conclusions: In this nationwide VA cohort consisting of nearly 1 million Veterans, smoking duration performed at least as well as TPY in predicting lung cancer risk and substantially expanded screening eligibility with fewer missed cancers. TSD criteria were also associated with improved equity. These findings support revisiting national lung cancer screening guidelines to prioritize smoking duration over pack-years.