A new paper in the Journal of the National Cancer Institute finds that eliminating the race disparity in colon cancer testing in the United States would dramatically reduce colon cancer, and colon cancer death rates, among Black people.

Colorectal cancer rates and deaths from the disease have decreased over time, but racial disparities remain and are significant. Compared to white Americans, Black Americans experience higher rates of colorectal cancer incidence and lower survival rates. Black adults are approximately 23% more likely to receive a colorectal cancer diagnosis than white adults. They are also about 31% more likely to die from the disease.

Researchers have previously identified screening adherence as the main driver of racial disparities in colorectal cancer incidence and mortality. A 2005 study using data from the National Health Interview Survey of adults over 50 showed that 52% of white people were up to date on colorectal cancer screenings but only 39% of Black people were up to date.

The gap has narrowed in recent years and rates have improved overall. In 2019, 69.5% of Black people and 69.8% of white people were keeping up with their screenings. Yet persistent Black-white disparities in colorectal cancer incidence, mortality, and survival remain.

The benefits of colorectal cancer screening programs rely on patients completing a follow-up colonoscopy if doctors first discover an abnormal result in the initial non-colonoscopy test patients over 50 get as part of their normal treatment. The quality of a colonoscopy screening is also particularly important.

Existing data demonstrates significantly lower follow-up colonoscopy rates among Black patients. But even if Black-white disparities in the receipt of colonoscopy screening are small, disparities in outcomes can still be substantial. Black adults are more likely than white adults to receive a low-quality colonoscopy.

The researchers here investigated these other racial disparities between Black and white Americans related to colorectal cancer. Using previously established and validated mathematical cancer models as their analysis platform, the researchers simulated screening follow-ups and colonoscopy quality rates in Black people to match those of white people to estimate how colorectal cancer outcomes could change with improvements in care and treatment.

They found that eliminating Black-white disparities in follow-up colonoscopy rates would reduce colorectal cancer incidence by 5.2%, and eliminating Black-white disparities in follow-up colonoscopy rates would reduce colorectal cancer mortality by 9.3%. The team also found that eliminating Black-white disparities in colonoscopy quality would reduce both colorectal cancer incidence and mortality by 9.4%. Eliminating differences in both follow-up rates and colonoscopy quality would reduce colorectal cancer incidence by 14.6% and colorectal cancer mortality by 18.7%.

Eliminating differences in both follow-up rates and colonoscopy quality would reduce the colorectal cancer incidence gap between Black and white people by 49%. Such changes would reduce the racial colorectal cancer mortality gap by 59%.

In this model, the elimination of the Black-White disparities in colonoscopy quality and follow-up colonoscopy rates would still not improve outcomes among Black adults to match those of white adults. The researchers believe this remaining gap is due to Black-white differences in general health and how patients receive treatment.

“People have long known that racial disparities in cancer exist,” said the paper’s lead author, Oguzhan Alagoz. “Usually, the focus has been on eliminating differences in adherence to screening, which reduces cancer deaths. However, our study shows that it’s not enough to just get everyone screened; the quality of care during screening and follow-up must also be similar for Black and white adults. To truly close the racial gap in cancer deaths and achieve health equity, we need to find innovative solutions.”