Association between Improved Colorectal Screening and Racial Disparities

To the Editor:

Attaining health equity is a national priority, but few examples exist of evidence-based interventions that eliminate health disparities.^1,2 We evaluated the association between participation in colorectal cancer screening and age-standardized incidence rates and mortality from 2000 through 2019 among non-Hispanic Black (hereafter Black) and non-Hispanic White (hereafter White) persons 50 to 75 years of age who were members of the Kaiser Permanente Northern California (KPNC) health plan. We extended follow-up through age 79 to account for lagged screening health outcomes. From 2006 through 2008, KPNC initiated (and has since sustained) an organized, population-based colorectal cancer screening program using proactive mailed fecal immunochemical testing annually and on-request colonoscopy.^3,4

Figure 1. Figure 1. Colorectal Cancer Screening Outcomes among Black Persons and White Persons in an Organized, Multilevel Continuum-of-Care Screening Program, 2000–2019.

Data are from a screening program piloted in 2006 through 2007 and fully implemented by 2008. Shown are the percentage of non-Hispanic White persons and non-Hispanic Black persons who were up to date on screening between 2000 and 2019 (Panel A), the incidence of 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 any-stage (Panel D) colorectal cancer, and colorectal cancer mortality (Panel E). 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 2000 U.S. Standard Population in 5-year age groups. Panel A shows that as organized screening rolled out, the percentage of persons who were up to date with screening became higher among White persons than Black persons by 5 percentage points, possibly because tools used early in the program may not have specifically addressed needs unique to Black persons for completing screening. The difference that emerged subsequently narrowed, but a small difference persisted throughout the study period. The y axis in Panels B, C, D, and E represents 3-year rolling averages based on 3-year total cumulative cases and person-years (e.g., the rates for 2003 represent the average of the incidence or mortality for 2001, 2002, and 2003; therefore, the incidence and mortality for 2000 and 2001 are not shown). The vertical line at 2006 in each panel indicates the first year of the screening program.

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

In concordance with enhanced detection from increased screening (Fig. S1), the incidence (expressed as a 3-year rolling average) of colorectal cancer among Black persons increased from 122 cases per 100,000 in 2002 to 166 per 100,000 in 2010; among White persons, the incidence was 118 cases per 100,000 in 2002 and was relatively stable until 2007 and then increased to 135 per 100,000 in 2009. The incidence subsequently declined markedly to 78 cases per 100,000 among White persons and 82 cases per 100,000 among Black persons during 2017 through 2019. In a finding consistent with earlier detection, the incidence of early-stage colorectal cancer initially increased in both groups, followed by decreases in both early- and late-stage cancers. The initial increases and later decreases were greater among Black persons.

Of note, we found tandem decreases in colorectal cancer–specific mortality in both groups — 54 cases per 100,000 among Black persons during 2007 through 2009 to 21 cases per 100,000 during 2017 through 2019 and 33 cases per 100,000 among White persons during 2007 through 2009 to 20 cases per 100,000 during 2017 through 2019 (Figure 1). The corresponding absolute between-group difference in mortality decreased markedly 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 probably resulted from 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 produced greater benefits among Black persons, probably owing to higher baseline incidence rates and mortality. The tools used in the program may not have addressed the needs unique to various populations for completing screening, which may have contributed to small, persistent between-group differences in the percentage of members who were up to date on screening. Concordant with U.S. national rates, colorectal cancer incidence rates and mortality were initially higher among Black persons than among White persons, despite comparable low-to-moderate screening rates; these higher rates may have resulted from differences in screening methods and quality and differences in follow-up and treatment for positive results.^3,4 The screening program strategies addressed such potential differences in care: centralized tracking increased screening participation and follow-up to close care gaps between Blacks and Whites.³ Also, on-demand sigmoidoscopy and guaiac fecal occult blood testing were replaced with a more effective and proactive strategy of fecal immunochemical testing and colonoscopy.

These results occurred within a health care system that serves patients who closely approximate the region’s underlying population, including people insured by Medicaid and Medicare, and thus support the principle that sustained efforts to intentionally enable equitable delivery of effective interventions across the care continuum can decrease, or even eliminate, related health disparities over time.^2,5

Chyke A. Doubeni, M.D., M.P.H.
Mayo Clinic, Rochester, MN

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

Wei Zhao, M.P.H.
Kaiser Permanente Medical Center, Walnut Creek, CA

YanKwan Lau, Ph.D., M.P.H.
Mayo Clinic, Rochester, MN

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