Racial disparities in colorectal cancer

What are the racial disparities in colorectal cancer?

A 2021 review investigated racial and ethnic disparities in colorectal cancer incidence and mortality among U.S. citizens. The review noted that Black Americans had the highest reported rates of CC incidence and mortality, while Native Americans had the second highest rates, compared to the following races:

• White Americans
• Hispanic Americans
• Asian Americans and Pacific Islanders

According to an earlier 2018 review, Black Americans have an incidence rate of CC that is at least 20% greater than that of White Americans. Black Americans are also more likely to have advanced disease at the time of diagnosis.

Researchers are still investigating the mechanisms underpinning the higher incidence of CC among certain races. However, two key factors that may contribute to these disparities are environment and genetics.

Environment

According to the 2021 review, structured societal issues, such as low socioeconomic status and a lack of medical insurance, may play a role in racial disparities in CC. These factors can lead to the following issues, which may contribute to the development of CC:

• poor nutrition
• tobacco use
• alcohol use

Another factor is a lower likelihood of CC screening among Black Americans.

The review notes that around 65% of the racial disparities in CC are due to environmental factors, with the remaining 35% being attributable to genetic factors.

Genetics

Black Americans are more likely to have advanced CC at the time of diagnosis. A 2018 review suggests this may be partly due to the fact that CC disproportionately affects the proximal colon in Black Americans. The proximal colon refers to the beginning and middle sections of the colon. Doctors can miss tumors in this section of the colon when screening for cancer.

In addition, the 2021 review notes that mutations to the genes EPHA6, FLCN, and HTR1F may contribute to the development of CC. The reviewers note that one study identified these mutations exclusively in Black Americans.

The 2021 review adds that while Black Americans appear to have the highest genetic susceptibility to CC, they are less likely to participate in CC screening.

Rates of colorectal cancer

A review in the journal Advances in Cancer Research estimated that in 2021, CC would affect 149,500 Americans and cause 52,980 deaths.

Rates of colorectal cancer are rising, though fatality rates appear to be falling slightly. According to the National Cancer Institute (NCI), experts estimate there will be more than 153,000 new cases of colorectal cancer in 2023 and approximately 52,550 deaths.

The NCI provides statistics on CC rates from 2000–2020 according to race and ethnicity. According to these statistics, CC rates are highest among Black Americans and Native Americans and are lowest among Asian and Pacific Islanders and Hispanic Americans.

Disparities

The following table is adapted from an article in Advances in Cancer Research and shows racial disparities in CC among five racial groups in the U.S. The figures represent the number of individuals per 100,000 people.

The data spans 2000–2018.

Researchers have further analyzed the above data to identify other racial disparities in CC rates, including disparities in CC onset, diagnosis, and outcome.

Disparities in onset

Compared to White Americans, Black Americans are typically younger at the time of diagnosis for CC.

Among females, the median age at diagnosis is 70 years for Black American females and 77 years for White American females. Among males, the median age at diagnosis is 66 years for Black American males and 72 years for White American males.

Compared to White Americans, Black Americans are twice as likely to receive a diagnosis of CC before the age of 50.

Disparities in diagnosis

Colorectal cancer affects the proximal colon more often in Black Americans than in other races. Cancers in the proximal colon can prove more challenging to identify during a colonoscopy. This may be one reason Black Americans tend to have more advanced disease at the time of diagnosis.

Disparities in outcome

The outcome for Black Americans living with CC is significantly worse than for people of other races living with this disease.

Overall, the death rate from CC has dropped since the beginning of the 21st century. Despite this, the death rate for Black Americans with CC remains 35% higher than that for White Americans with CC.

Researchers have not yet identified the reason for the racial disparity in disease outcomes for CC, although factors such as socioeconomic status and access to health insurance and treatment likely play a role.

Researchers need to continue studying factors affecting CC mortality rates, particularly among Black Americans and Native Americans.

Addressing the disparities

The racial disparity in CC incidence appears in Black Americans younger than 45 years of age. However, typical screening for CC used to begin at 50 years of age. A recent update to CC screening guidelines by the U.S. Preventive Services Task Force suggests that screening should begin at the age of 45 for everyone.

Scientists must also conduct further research into the exact causes of earlier CC incidence and increased mortality among different races. Identifying and addressing modifiable risk factors may help reduce the burden of CC among Black Americans and Native Americans.

It is also necessary to increase awareness of racial disparities of CC within communities. Doing so may encourage people to communicate their concerns to their doctors and undergo earlier screening.

The American Cancer Society already advocates for earlier screening among people with an average risk of developing CC. However, earlier and more frequent screening may be necessary for people at high risk of developing this disease.

Summary

In the U.S., there is significant racial disparity in rates of colorectal cancer (CC) incidence and mortality. When comparing the major racial and ethnic groups in the U.S., Black Americans have the highest rates of CC and Native Americans have the second highest rates.

Researchers believe that the racial disparity in CC is largely attributable to socioeconomic and environmental factors. Genetics also appear to play a role but to a lesser degree.

Researchers are continuing to investigate the factors contributing to the racial disparity in CC incidence and mortality. Until researchers identify these risk factors and policymakers address these issues, at-risk racial groups may require earlier and more frequent screening for CC.