Colon cancer (CRC) is the second leading cause of cancer death in both men and women in the United States. Thanks in large part to the increased screening of those over 50 over the past decade, CRC rates have declined in the general population as a whole. However, the incidence of CRC in younger people in the United States is increasing at an alarming rate. Over the past 20 years, the CRC rate in people under the age of 50 has increased by 2.2% per year. Hidden in these statistics are the significant differences in CRC incidence and outcomes for African Americans.
Compared to whites, African Americans have a 20% higher incidence of CRC. They are more likely to develop CRC at a younger age, be further diagnosed with their disease, and more likely to die from their disease. African Americans have the lowest 5-year survival rate for CRC of any racial group in the United States. The absolute rates of early onset CRC, commonly defined as CRC diagnosed before age 50 to 55, are higher in African Americans than in whites. The recent deaths of Chadwick Boseman, aged 43, and Natalie Desselle-Reid, aged 53, are tragic examples of the disproportionate impact of early-onset CRC in the African American community.
Inequalities contribute to many factors that can increase the risk of early-onset CRC
The reasons for these racial differences in early onset CRC are unclear. This is not surprising as we do not collectively understand the factors that increase the increased incidence of early onset CRC in all races.
Some factors that have been linked to early onset CRC are obesity, physical inactivity, and unhealthy eating habits. According to a survey by the National Institutes of Health / AARP, any of these risk factors may be more common in African American communities, especially those with low socioeconomic status. African Americans also have less access to health care. As a result, they may not be able to see a doctor right away to manage symptoms related to colorectal polyps or cancer. This, in turn, could delay the detection of tumors that could be cured by removal by colonoscopy or surgery if detected early enough. For unclear reasons, African Americans are less likely to receive chemotherapy or surgery after diagnosis than white patients.
Underlying these possible explanations are widespread inequalities based on socio-economic status and systemic racism.
Biological characteristics related to disparities
African Americans are also more likely to be diagnosed with CRC that originated in the right colon rather than the left colon or rectum. As I noted in a previous blog post, colon cancers on the right side may be more difficult to spot and have a poorer prognosis compared to CRCs on the left side.
Recent studies suggest that differences in the epigenome of the right colon compared to the left colon in African Americans compared to the pattern observed in whites could explain racial differences at the point where CRCs originate. (An epigenome is made up of chemical compounds that attach to a person’s DNA and affect its expression.) Some data suggest that the molecular profile of tumors that develop in African Americans may be different compared to whites, which Pointing out the initiating pathways or promoting the progression of cancer can vary by race. Differences in gut microbiome have increasingly been associated with the increasing incidence of early onset CRC and may also contribute to a higher incidence of CRC in African Americans.
Updated screening guidelines can leave African Americans behind
Until recently, most expert panels did not generally recommend CRC screening for those at average risk under the age of 50. Only the American College of Gastroenterology and the American Society for Gastrointestinal Endoscopy recommend earlier screening in African Americans. However, in 2018 the American Cancer Society (ACS) changed its guidelines to recommend starting screening for people of all races by the age of 45. In October 2020, the U.S. Preventive Services Task Force published draft recommendations based on ACS guidelines.
It is expected that these newer guidelines will have an impact on reducing the incidence of early onset CRC. However, significant concerns remain about the persistent differences between African Americans and whites in accessing and participating in CRC screening. In addition, CRC rates have risen sharply in people between the ages of 20 and 45. The revised guidelines do not apply to people in this age group.
Improvements in racial inequalities and systemic racism, as well as medical advances, were needed to fill gaps in the early-onset CRC
With the increasing attention to early onset CRC and the long-standing problem of racial disparities in the incidence and outcomes of CRC, hopefully significant progress will be made in the coming years in addressing these converging public health priorities. This should include further research into the causes of early onset CRC, improving early detection through screening and prevention, and ensuring access to effective treatment. With socio-economic and racial inequalities at the root of many CRC disparities, there remains a great unmet need for the medical and public health communities to address these broader issues.
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