Trends in lung adenocarcinoma incidence among younger adults in the United States: A SEER-based Joinpoint analysis.

e20113 Background: Patterns of lung adenocarcinoma (LUAD) incidence among younger adults remain underexplored, particularly across racial and ethnic subgroups. We sought to evaluate long-term incidence trajectories by stage, sex, and race/ethnicity to identify populations with emerging risk. Methods: Using SEER 17 Registries (Nov 2023 submission), we identified LUAD cases diagnosed between 2000–2021 in patients aged 15–49. Age-adjusted incidence rates were calculated with the 2000 US standard population. Cases were stratified by age (15–39 vs 40–49), sex, race/ethnicity (NHW, NHB, NHAPI, Hispanic), and stage (localized, regional, distant). Joinpoint regression estimated annual percent change (APC) and average annual percent change (AAPC). Statistical significance was defined as p-value < 0.05. Results: Overall cancer incidence among individuals aged 15–39 years remained stable during the study period (AAPC –0.47, p = 0.39). When stratified by race/ethnicity, a modest but statistically significant decline was observed among non-Hispanic White individuals (AAPC –1.506, p = 0.047), whereas incidence trends among non-Hispanic Black (AAPC +0.99, p = 0.43) and Hispanic populations (AAPC +1.656, p = 0.266) did not demonstrate significant changes. Stage-specific analyses showed a significant decline in regional-stage disease overall (AAPC –4.44, p = 0.025). In contrast, trends in localized and distant-stage incidence were not statistically significant across the overall population or when stratified by sex and race/ethnicity. Sex-specific analyses similarly revealed no significant changes in overall incidence among males or females. Among individuals aged 40–49 years. Non-Hispanic White (AAPC –3.59, p < 0.001) and non-Hispanic Black populations (AAPC –4.25, p < 0.001) demonstrated significant decreases, while Hispanic incidence remained stable (AAPC –0.87, p = 0.18). Notably, non-Hispanic Asian or Pacific Islander females exhibited a significant increase in distant-stage incidence (AAPC +2.41, 95% CI 0.66–4.22, p = 0.007). Regional-stage incidence declined across most groups (AAPC –6.53, p < 0.001). Conclusions: Lung adenocarcinoma incidence among younger adults has remained largely stable over the past two decades. A modest but significant decline was observed among non-Hispanic White individuals and in regional-stage disease, while no significant temporal changes were identified across other racial/ethnic, sex-specific, or stage-specific subgroups. Continued surveillance is warranted to monitor potential emerging disparities in this population.