Association between Improved Colorectal Screening and Racial Disparities

About the publisher:

Achieving health equity is a national priority, but examples of evidence-based interventions that address health inequalities are few.1.2 We analyzed the association between colorectal cancer screening attendance and age-standardized incidence rates and mortality from 2000 to 2019 among non-Hispanic black (hereinafter “Black”) and non-Hispanic white (hereinafter “White”) people aged 50 to 75 years, the members were assessed by the Kaiser Permanente Northern California (KPNC) health plan. We extended follow-up to age 79 to account for delayed health outcomes from screening. From 2006 to 2008, KPNC initiated (and has since maintained) an organized, population-based colorectal cancer screening program that uses proactive, mailed stool immunochemistry testing and an on-demand colonoscopy.3.4

Colorectal cancer screening outcomes in blacks and whites in an organized, multi-stage continuum of care screening program, 2000–2019.

The data comes from a screening program that was piloted in 2006-2007 and fully implemented by 2008. Shown is the percentage of non-Hispanic White and non-Hispanic Black people who were to date between 2000 and 2019 (Panel A). Incidence at early stage (Panel B), late stage (Panel C; includes regional spread with nodal involvement or distant disease as defined using codes 3, 4, or 7 from the SEER Program Coding and Staging Manual), and each stage (Panel D) Colorectal cancer and colorectal cancer mortality (panel E). The shaded areas in panels B, C, D, and E represent 95% confidence intervals. Colorectal cancer incidence rates and mortality (per 100,000) are age-standardized to the US standard population of 2000 in 5-year age groups. Panel A shows that with the advent of organized screening, the percentage of people up to date with screening was 5 percentage points higher for Whites than Blacks, possibly because tools used early in the program may not Special attention was paid to the special needs of Black people for the completion of the screening. The difference found later decreased, but a small difference remained throughout the study period. The y-axis in panels B, C, D, and E represents 3-year moving averages based on 3-year cumulative cases and person-years (e.g., 2003 rates represent the average of incidence or mortality for 2001, 2002, and 2003; therefore incidence and mortality are not shown for 2000 and 2001). The vertical line at 2006 in each box indicates the first year of the screening program.

In a dynamic cohort that increased to 88,734 Black and 703,347 White individuals by 2019 (Table S1 in the Supplementary Appendix, available with the full text of this letter at NEJM.org), the percentage up to date with screening increased, from 42% in 2000 to 79-80% in 2015-2019 among blacks and from 40% in 2000 to 82-83% in 2015-2019 among whites (Figure 1A and Table S2).

Consistent with improved detection through increased screening (Fig. S1), the incidence (expressed as a 3-year moving average) of colorectal cancer in blacks increased from 122 cases per 100,000 in 2002 to 166 per 100,000 in 2010; among whites, the incidence was 118 cases per 100,000 in 2002 and was relatively stable until 2007, when it rose to 135 per 100,000 in 2009. Thereafter, the incidence dropped significantly to 78 cases per 100,000 among whites and 82 cases per 100,000 among blacks in 2017-2019. In a finding consistent with earlier detection, the incidence of early-stage colorectal cancer initially increased in both groups , followed by a decline in both early- and late-stage cancer. Initial increases and later decreases were greater in blacks.

Notably, we found a simultaneous decrease in colorectal cancer-specific mortality in both groups — from 54 cases per 100,000 in blacks in 2007-2009 to 21 cases per 100,000 in 2017-2019 and 33 cases per 100,000 in whites in 2007-2009 20 cases per 100,000 in 2017-2019 (illustration 1). The corresponding absolute difference between groups in mortality decreased significantly from 21.6 cases per 100,000 (95% confidence interval [CI]9.8 to 33.5) to 1.6 cases per 100,000 (95% CI, -4.9 to 8.1).

These improvements likely result from the equitable delivery of effective strategies across the screening continuum, including prevention through polyp removal, earlier detection of treatable cancers, and more timely treatments. Such uniform improvements led to greater benefits among blacks, likely due to higher baseline incidence rates and mortality. The tools used in the program may not have addressed the needs of different populations at the completion of screening, which may have contributed to small, persistent differences between groups in the percentage of members up to date at screening. Consistent with US national rates, colorectal cancer incidence rates and mortality were initially higher among blacks than whites, despite comparably low to moderate screening rates; These higher rates could be due to differences in screening methods and quality, as well as differences in follow-up and treatment of positive outcomes.3.4 The strategies of the screening program addressed such potential differences in care: centralized follow-up, increased screening attendance, and follow-up to close gaps in care between blacks and whites.3 In addition, on-demand sigmoidoscopy and Guaiac stool occult blood testing have been replaced by a more effective and proactive strategy of immunochemical stool testing and colonoscopy.

These results were achieved in a health care system that cares for patients very similar to the Region’s underlying population, including Medicaid and Medicare beneficiaries, and thus support the principle that sustained efforts to intentionally ensure equitable delivery of effective interventions across the continuum of care to enable, decrease, or even eliminate, related health inequalities over time.2.5

Chyke A. Doubeni, MD, MPH
Mayo Clinic, Rochester, MN

Douglas A. Corley, MD, Ph.D.
Kaiser Permanente Research Division, Oakland, CA
[email protected]

Wei Zhao, MPH
Kaiser Permanente Medical Center, Walnut Creek, CA

YanKwan Lau, Ph.D., MPH
Mayo Clinic, Rochester, MN

Christopher D. Jensen, Ph.D.
Theodore R. Levin, MD
Kaiser Permanente Medical Center, Walnut Creek, CA

Supported by the National Cancer Institute from the National Institutes of Health (Award Numbers R01CA213645 and R37CA222866). The funding source played no role in the design and conduct of the study or the decision to submit the manuscript for publication.

Disclosure forms provided by the authors with the full text of this letter are available at NEJM.org.

dr Doubeni and Corley contributed equally to this letter.

  1. 1. U.S. Task Force on Preventive Services, Davidson KW, Mangione CM, et al. Actions to Transform U.S. Preventive Services Task Force Methodologies to Reduce Systemic Racism in Clinical Preventive Services. JAMA 2021;326:24052411.

  2. 2. Doubeni CA, Selbi K, Gupta S. Frameworks and strategies for eliminating disparities in colorectal cancer screening outcomes. Year Rev. Med 2021;72:383398.

  3. 3. Selbi K, Jensen CD, Levin TR, et al. Program components and outcomes of an organized colorectal cancer screening program with annual immunochemical stool testing. Clin Gastroenterol Hepatol 2022;20:145152.

  4. 4. Mehta SJ, Jensen CD, Quinn Vice President, et al. Race/Ethnicity and Adoption of a Population Health Management Approach to Colorectal Cancer Screening in a Community Health System. J Gen Internal Med 2016;31:13231330.

  5. 5. Laiyemo AO, Doubeni C, Pinsky PF, et al. Racial and colorectal cancer differences: health care utilization vs differential cancer susceptibility. J National Cancer Inst 2010;102:538546.