Abstract PO-223: Examining racial differences in metastatic site and mortality among de novo stage IV colorectal cancer
Authors: Dhar Sakshi M. , Han Yunan , Toriola Adetunji 
Published: January 2022

Background: Racial disparities persist in colorectal cancer (CRC) incidence and survival despite advances in screening and therapeutic options. While the liver and lung are often described as common sites for CRC metastasis, the effect of race and ethnicity on the presentation of metastases remains largely unexplored. In this study, we investigate the racial differences in metastatic patterns of de novo stage IV CRC and associate these patterns with racial differences in CRC mortality. Methods: This retrospective cohort study used 18 Surveillance, Epidemiology and End Results (SEER) registries with data from 2010-2017 to identify 49,654 patients diagnosed with de novo metastatic, stage IV CRC. We evaluated the pattern of bone, lung, liver and brain metastases by race and ethnicity. Using multi-variate logistic regression, we obtained adjusted odds ratios (aOR) to estimate the association between metastatic pattern and race and ethnicity. We assessed the adjusted hazard ratios (aHR) for CRC-specific mortality and all-cause mortality by race and ethnicity using Cox proportional hazards regression models. Results: Of 49,654 patients, 63.5% were non-Hispanic White (NHW), 14.81% were NHB, and 12.6% were Hispanic. Majority of metastases were within the liver (72.3%) and lung (24.7%). The odds of metastasis to the liver was 1.13 times higher (95% CI, 1.06-1.20) and the odds of metastasis to lung was 1.19 times higher (95% CI, 1.09-1.23) in NHB than NHW patients. The odds of metastasis at any site was 1.19 times higher in NHB than NHW patients (95% CI, 1.10-1.28). The odds of metastasis to multiple sites was 1.16 times higher than to a single site for a NHB patient (95% CI, 1.09- 1.24). NHB patients had a higher adjusted hazard ratio of CRC-specific mortality when compared to NHW patients, overall (aHR 1.15, 95% CI 1.12-1.19); and when looking specifically at metastasis to the lung (aHR 1.10, 95% CI 1.04-1.16) and the liver (aHR 1.17, 95% CI 1.13-1.21). NHB had a 14% increased risk of mortality with metastases to multiple sites (aHR 1.14, 95% CI 1.07-1.121). Conclusion: In this retrospective cohort study, NHB patients presented more frequently with metastases at diagnosis and had higher odds of multiple metastases at diagnosis than their NHW counterparts, placing these patients at a higher risk of mortality. This study quantifies the ongoing severity of racial disparity that persists despite advances in CRC diagnostics and therapeutics. Targeted effort is needed at the prevention, screening and therapy levels, to create equity and improve CRC outcomes for the NHB patient population.

Citation Format: Sakshi M. Dhar, Yunan Han, Adetunji Toriola. Examining racial differences in metastatic site and mortality among de novo stage IV colorectal cancer [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-223.