Black-White disparities in colorectal cancer outcomes: a simulation study of screening benefit.

The US Black population has higher colorectal cancer (CRC) incidence rates and worse CRC survival than the US White population, as well as historically lower rates of CRC screening. The Surveillance, Epidemiology, and End Results incidence rate data in people diagnosed between the ages of 20 and 45 years, before routine CRC screening is recommended, were analyzed to estimate temporal changes in CRC risk in Black and White populations. There was a rapid rise in rectal and distal colon cancer incidence in the White population but not the Black population, and little change in proximal colon cancer incidence for both groups. In 2014-2018, CRC incidence per 100 000 was 17.5 (95% confidence interval [CI] = 15.3 to 19.9) among Black individuals aged 40-44 years and 16.6 (95% CI = 15.6 to 17.6) among White individuals aged 40-44 years; 42.3% of CRCs diagnosed in Black patients were proximal colon cancer, and 41.1% of CRCs diagnosed in White patients were rectal cancer. Analyses used a race-specific microsimulation model to project screening benefits, based on life-years gained and lifetime reduction in CRC incidence, assuming these Black-White differences in CRC risk and location. The projected benefits of screening (via either colonoscopy or fecal immunochemical testing) were greater in the Black population, suggesting that observed Black-White differences in CRC incidence are not driven by differences in risk. Projected screening benefits were sensitive to survival assumptions made for Black populations. Building racial disparities in survival into the model reduced projected screening benefits, which can bias policy decisions.

The impact of cumulative colorectal cancer screening delays: A simulation study.

OBJECTIVE: Annual fecal immunochemical tests can reduce colorectal cancer incidence and mortality. However, screening is a multi-step process and most patients do not perfectly adhere to guideline-recommended screening schedules. Our objective was to compare the reduction in colorectal cancer incidence and life-years gained based on US guideline-concordant fecal immunochemical test screening to scenarios with a range of delays. METHOD: The Colorectal Cancer Simulated Population model for Incidence and Natural history (CRC-SPIN) microsimulation model was used to estimate the effect of systematic departures from fecal immunochemical test screening guidelines on lifetime screening benefit. RESULTS: The combined effect of consistent modest delays in screening initiation (1 year), repeated fecal immunochemical test screening (3 months), and receipt of follow-up or surveillance colonoscopy (3 months) resulted in up to 1.3 additional colorectal cancer cases per 10,000, 0.4 additional late-stage colorectal cancer cases per 10,000 and 154.7 fewer life-years gained per 10,000. A 5-year delay in screening initiation had a larger impact on screening effectiveness than consistent small delays in repeated fecal immunochemical test screening or receipt of follow-up colonoscopy after an abnormal fecal immunochemical test. The combined effect of consistent large delays in screening initiation (5 years), repeated fecal immunochemical test screening (6 months), and receipt of follow-up or surveillance colonoscopy (6 months) resulted in up to 3.7 additional colorectal cancer cases per 10,000, 1.5 additional late-stage colorectal cancer cases per 10,000 and 612.3 fewer life-years gained per 10,000. CONCLUSIONS: Systematic delays across the screening process can result in meaningful reductions in colorectal cancer screening effectiveness, especially for longer delays. Screening delays could drive differences in colorectal cancer incidence across patient groups with differential access to screening.