Abstract B166: Impact of rurality on early-onset colorectal cancer outcomes: Age, geographic disparities, and the need for improved access and awareness in the United States

Abstract BACKGROUND: While overall colorectal cancer (CRC) rates have stabilized or declined in the United States (U.S.), early-onset CRC (EO-CRC), diagnoses before age 50, has increased. Rural U.S. residents face a higher CRC incidence (43.9 vs. 40.1 per 100,000) than urban residents. CRC mortality, once highest in the Northeast, is now most prevalent in the South and Midwest, particularly among Non-Hispanic Black populations. This geographic shift is also evident in EO-CRC. Existing literature lacks comprehensive analysis on the influence of rurality and age at CRC diagnosis. In this study, we sought to elucidate the relationships between age at diagnosis with CRC outcomes, while examining the moderating role of rurality. Methods: We used data from the 2006-2020 Surveillance, Epidemiology, and End Results (SEER) Program. Rurality was defined using census tract level U.S. Department of Agriculture (USDA)’s 2010 Rural Urban Commuting Area (RUCA) codes: rural (codes 8, 9, 10) and urban (all other listed codes). We conducted multilevel regression modeling (logistic and Cox proportional hazards) to examine the associations between age at diagnosis, rurality, and CRC outcomes (late-stage diagnosis and survival), adjusting for race, marital status, sex, and year of diagnosis. Results: We identified 835,907 patients aged 20-79 from the 2006-2020 SEER program. Most patients lived in urban areas (86%), were non-Hispanic white (66%), and married (41%). After adjusting for marital status, race, sex, and diagnosis year, we found that patients aged 30-39 (aOR: 1.49, 95% CI: 1.44–1.55) and 40-49 (aOR: 1.43, 95% CI: 1.39–1.46) had over a 40% increased likelihood of late-stage CRC compared to patients aged 50-59. Urban patients aged 30-39 had a 52% higher likelihood of late-stage CRC (aOR: 1.52, 95% CI: 1.46–1.58). Patients aged 20-29 (aOR: 0.81, 95% CI: 0.77–0.86) had a reduced risk of CRC death compared to those aged 50-59. Conversely, patients aged 40-49 (aOR: 1.09, 95% CI: 1.07–1.11), 60-69 (aOR: 1.16, 95% CI: 1.14–1.17), and 70-79 (aOR: 1.39, 95% CI: 1.28–1.36) had increased risks of CRC death compared to patients aged 50-59. Rural patients aged 20-29 (aOR: 0.79, 95% CI: 0.68–0.94) and 30-39 (aOR: 0.95, 95% CI: 0.87–1.03) had a reduced risk of CRC death compared to rural patients aged 50-59. Conclusion: We observed that patients aged 30-49 were more likely to be diagnosed with late- stage CRC compared to those aged 50-59, particularly in urban areas. To reduce the burden of EO-CRC and prevent advanced-stage diagnoses in young adults, it is essential to enhance access to care and raise awareness of CRC symptoms among younger Americans. Future research should explore urban -rural barriers to healthcare access, including the role of healthcare infrastructure, transportation, and provider availability, to develop strategies for improving EO-CRC early detection and treatment outcomes. Citation Format: Meng-Han Tsai, Justin X. Moore, Caitlyn Grunert. Impact of rurality on early-onset colorectal cancer outcomes: Age, geographic disparities, and the need for improved access and awareness in the United States [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr B166.