Background There are well‐established disparities in colorectal cancer (CRC) outcomes between White and Black patients; however, assessments of CRC disparities for other racial/ethnic groups are limited. Methods The Surveillance, Epidemiology, and End Results database identified patients aged 50–74 years with CRC adenocarcinoma from 2000 to 2019. Trends in age‐adjusted incidence rates were computed by stage at diagnosis and subsite across five broad race/ethnic groups (White, Black, Asian/Pacific Islander [API], American Indian/Alaskan Native [AIAN], and Hispanic) and four API subgroups (East Asian, Southeast Asian, South Asian, and Pacific Islander) Multivariable logistic regression evaluated associations between race/ethnicity and diagnosis stage. Multivariable Cox proportional hazards models assessed differences in cause‐specific survival (CSS). Results Hispanic, AIAN, Southeast Asian, Pacific Islander, and Black patients were 3% to 28% more likely than Whites to be diagnosed with distant stage CRC, whereas East Asian and South Asians had similar or lower risk of distant stage CRC. From Cox regression analysis, Black, AIAN, and Pacific Islanders also experienced worse CSS, while East Asian and South Asian patient groups experienced better CSS. No significant differences in CSS were observed among Hispanic, Southeast Asian, and White patients. When stratified by stage, Black patients had worse CSS across all stages (early, hazard ratio (HR) = 1.38; regional, HR = 1.22; distant, HR: 1.07, p < 0.05 for all). Conclusion Despite advances in CRC screening, treatment and early detection efforts, marked racial/ethnic disparities in incidence, stage at diagnosis, and survival persist. Findings demonstrate the extent to which aggregating heterogenous populations masks significant variability in CRC outcomes within race/ethnic subgroups.
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<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<0.001) and distal colon (IRR=1.51, p<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.
Over the past 21 years, while the incidence of colorectal cancer in the US has decreased, disparities in race and ethnicity have increased but no recent evaluation exists of differences in race and ethnicity by location of primary tumors within the colon and rectum among all age groups. Recent literature has shown that there are differences in the rates of colorectal cancer between multiple minority groups; however, many of these studies only compare CRC among White and Black groups. We examined the trends of colorectal cancer incidence by racial/ethnic group and location of the primary tumors within the colon and rectum to describe disparities. This study used SEER*Stat v 8.3.9 Incidence – SEER Research Data, 18 Registries, Nov 2020 Sub (2000-2018) to analyze age-adjusted rates in incidence by race, ethnicity, sex, and site. We examined the sites within the proximal, transverse, and distal colon, as well as the rectum, and further examined localized, regional, and distant diagnosis stages. As others have reported, we observed declining incidence in colorectal cancer, but found that some racial and ethnic groups experienced higher incidence rates compared to other groups by diagnosis site and the stage of diagnosis. For example, when singling out the proximal colon, Black males had a rate of 12.7/100,000 people at the local stage in 2000. Comparing this localized proximal rate to male Whites (11.7), American Indian/Alaskan Natives (7.2), Asians/Pacific Islanders (6.9), and Hispanics (7.9), we can see that Blacks have already experienced a higher diagnosis rate than other races and ethnicities. Examining annual percent changes, incidence rates for Blacks decreased just as those for other racial and ethnic groups did. However, they do not experience the largest annual percent decrease. From this portion of the data, we see that some racial and ethnic groups had decreases in incidence trends. However, when examining each rate individually by subsite and diagnosis stage, some groups are seeing a trend where the rate is not as favorable. Despite declining incidence rates of colorectal cancer in the United States overall, comparisons by race and ethnicity reveal important disparities, particularly by site of primary tumors within the colon and rectum, which may have critical implications for treatment and long-term survival. Citation Format: Andrea Joyce M Malabay, Kristin Primm, Taylor Curry, Shine Chang. Examining disparities in incidence of colorectal cancer by race, ethnicity, sex, and site [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 PR-06.
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