Abstract A007: Trends and racial and ethnic disparities in colorectal cancer by anatomic subsite and stage at diagnosis, 2000-2019
Authors: Primm Kristin M. , Malabay Andrea , Curry Taylor , Chang Shine 
Published: December 2022

Introduction: Subsite-specific incidence rates (IRs) of colorectal cancer (CRC) vary considerably by race/ethnicity and patterns of stage at diagnosis by anatomic subsite may reflect access to CRC screening. We examine racial and ethnic trends and differences in CRC IRs by stage and subsite in a screening eligible population. Methods: The Surveillance, Epidemiology, and End Results 17 registries database identified 374,582 patients aged 50-74 diagnosed with adenocarcinoma CRC from 2000-2019. Stage-specific (In situ/localized, regional, distant), age-adjusted IRs were computed by subsite (proximal, distal, rectal) and race/ethnicity (White, Black, Asian/Pacific Islander [API], American Indian/Alaskan Native [AIAN], and Hispanic). Trends in IRs were measured using annual percentage change (APC) and absolute change. Proportional stage distribution (percent contribution of each cancer stage) were calculated and compared using chi-squared tests. Supplemental analyses compared differences in stage distribution within API subgroups (Filipino, Chinese, Japanese, Korean, Vietnamese, Pacific Islander). Results: From 2000-2019, IRs decreased across all CRC subsites and racial and ethnic groups except for AIAN patients. For AIAN patients, the incidence of rectal cancer increased over time (APC=1.24, p&lt;0.05), while IRs for proximal and distal colon cancer remained stable over time. When stratified by stage, the steepest percent decreases in IRs were among in situ/localized and regional stages, with smaller declines for distant stage tumors across all race/ethnic groups. As of 2018-2019, IRs of distant stage tumors of the proximal (IRR=2.09, p&lt;0.001) and distal colon (IRR=1.51, p&lt;0.001) cancers remained 1.5 to 2 times higher among Black patients compared to White patients, while API and Hispanic patients had similar or lower distant stage IRs for proximal and distal subsites. In contrast, stage-specific rectal cancer IRs were similar across race/ethnic groups. Proportional stage analysis revealed an increase in distant stage tumors and a decrease in in situ/localized stage tumors over time among distal colon and rectal subsites across all race/ethnic groups. As of 2018-2019, Black patients had higher percentages of distant stage tumors and lower percentages of in situ/localized tumors compared to other race/ethnic groups, and this was consistent across all three subsites. In supplemental analysis, Pacific Islander patients had higher percentages of distant stage CRC (22.6%), while Japanese patients had higher percentages of in situ/localized CRC (16.85%). Conclusions: Our findings suggest that racial and ethnic disparities in CRC vary by subsite, with Black patients experiencing higher rates of distant stage tumors of the proximal and distal colon. While decreases in CRC IRs highlight the positive impact of CRC screening and early detection efforts, more work is needed to reduce persistent disparities for Black patients. Variation by stage within API subgroups emphasizes the need to examine disparities among disaggregated racial and ethnic groups.

Citation Format: Kristin M. Primm, Andrea Malabay, Taylor Curry, Shine Chang. Trends and racial and ethnic disparities in colorectal cancer by anatomic subsite and stage at diagnosis, 2000-2019 [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr A007.