Abstract PR11: Racial differences in characteristics of early- vs. late-onset colorectal cancer among veterans
Authors: Chapman Monalesia , Williams Christina D. , Redding Thomas Ivey , Bartlett Robin , Chawla Neeta , Provenzale Dawn , Kelley Michael J. 
Published: August 2020

Abstract
Introduction: Colorectal cancer (CRC) accounts for approximately 8% of annual cancer cases in the Veterans Health Administration. While CRC incidence is decreasing, evidence suggests that the incidence among the subset of patients diagnosed before the age of 50 is increasing. The purpose of this work is to compare the clinical and demographic characteristics of veterans with early-onset CRC (age at diagnosis &lt;50; EOC) and late-onset CRC (age at diagnosis ≥50; LOC) and assess racial differences within both groups.
Methods: We conducted a retrospective analysis of national cohort data in the Veterans Affairs Central Cancer Registry on patients diagnosed with CRC between 2001 and 2011. Descriptive statistics (frequencies, medians) were used to compare characteristics among EOC and LOC patients and evaluate black-white differences within both groups of CRC patients.
Results: In this cohort of 31,435 patients, 3% (N=966) had EOC, and this proportion was consistent each year. Statistically significant differences between EOC and LOC were noted for race, stage, and tumor location (all p&lt;0.0001). The black/white race distribution was 33%/64% in EOC and 17%/80% in LOC. For stage, 56% of EOC and 44% of LOC were stage III/IV. Regarding tumor location, 39% of EOC was rectum whereas 30% of LOC was rectum. 5-year overall survival (OS) was 58% in EOC and 50% in LOC (p&lt;0.0001); however, no difference in CRC-specific survival was noted (72% vs 74%, p=.13). We also observed significant differences by race when comparing demographic and clinical characteristics within EOC and LOC. Race-specific results for EOC patients were as follows: Median age was 46 for both blacks and whites; the proportion of blacks diagnosed with Stage III/IV disease was 51% compared to 58% of whites (p=0.001); tumor location was rectum for 31% of blacks and 43% of whites (p=0.0006); and overall and CRC-specific survival rates were similar for blacks and whites. The following was observed among patients with LOC: Blacks were slightly younger than whites (median age 66 vs 69, respectively); stage III/IV disease was noted for 47% of blacks and 43% of whites (p&lt;0.0001); 24% of blacks and 31% of whites had rectum tumor location (p&lt;0.0001); and overall and CRC-specific survival rates were lower among blacks compared to whites.
Conclusion: Although we did not find an increasing proportion of EOC over time, EOC was more common in blacks than whites and more common in the distal large bowel. EOC in blacks, however, was more commonly proximal, had less advanced stage at diagnosis but similar survival compared to whites. EOC has distinct clinical characteristics in blacks that may reflect differences in molecular etiology. Our findings emphasize the importance of distinguishing between EOC and LOC to better understand the unique characteristics of early-onset disease and how they might inform prevention and early detection efforts.
This abstract is also being presented as Poster C116.
Citation Format: Monalesia Chapman, Christina D. Williams, Thomas Ivey Redding, Robin Bartlett, Neeta Chawla, Dawn Provenzale, Michael J. Kelley. Racial differences in characteristics of early- vs. late-onset colorectal cancer among veterans [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr PR11.