Incidentally Detected Lung Cancer in Persons Too Young or Too Old for Lung Cancer Screening in a Mississippi Delta Cohort.

Introduction: Lung cancer risk in screening age-ineligible persons with incidentally detected lung nodules is poorly characterized. We evaluated lung cancer risk in two age-ineligible Lung Nodule Program (LNP) cohorts.

Methods: Prospective observational study comparing 2-year cumulative lung cancer diagnosis risk, lung cancer characteristics, and overall survival between low-dose computed tomography (LDCT) screening participants aged 50 to 80 years and LNP participants aged 35 to younger than 50 years (young) and older than 80 years (elderly).

Results: From 2015 to 2022, lung cancer was diagnosed in 329 (3.43%), 39 (1.07%), and 172 (6.87%) LDCT, young, and elderly LNP patients, respectively. The 2-year cumulative incidence was 3.0% (95% confidence intervals [CI]: 2.6%-3.4%) versus 0.79% (CI: 0.54%-1.1%) versus 6.5% (CI: 5.5%-7.6%), respectively, but lung cancer diagnosis risk was similar between young LNP and Lung CT Screening Reporting and Data System (Lung-RADS) 1 (adjusted hazard ratio [aHR] = 0.88 [CI: 0.50-1.56]) and Lung-RADS 2 (aHR = 1.0 [0.58-1.72]). Elderly LNP risk was greater than Lung-RADS 3 (aHR = 2.34 [CI: 1.50-3.65]), but less than 4 (aHR = 0.28 [CI: 0.22-0.35]). Lung cancer was stage I or II in 62.92% of LDCT versus 33.33% of young (p = 0.0003) and 48.26% of elderly (p = 0.0004) LNP cohorts; 16.72%, 41.03%, and 29.65%, respectively, were diagnosed at stage IV. The aggregate 5-year overall survival rates were 57% (CI: 48-67), 55% (CI: 39-79), and 24% (CI: 15-40) (log-rank p < 0.0001). Results were similar after excluding persons with any history of cancer.

Conclusions: LNP modestly benefited persons too young or old for screening. Differences in clinical characteristics and outcomes suggest differences in biological characteristics of lung cancer in these three patient cohorts.