Studying Colorectal Cancer Within The Black Community

Drawing of colorectal cancer by 23andMe

In time for Colon Cancer Awareness Month, 23andMe launched its Genetic Insights into Colorectal Cancer in the Black Community study this week that we hope will help improve the performance of genetic report models that could help alert those with a higher likelihood of developing colorectal cancer.


March is Colon Cancer Awareness Month. Did you know that Colorectal cancer is one of the most common forms of cancer? It is also one of the leading cancer-related causes of death in the United States, according to the US Centers for Disease Control and Prevention. It’s impact on people of color is particularly pernicious because they tend to be diagnosed in later stages of cancer and often receive lower-quality care. That plays a big role in why.

Black and African American individuals are about 20 percent more likely to develop colorectal cancer and about 40 percent are more likely to die from it, according to the American Cancer Society.

With early detection, treatment is much more likely to succeed.  This is why screening — through colonoscopy or stool-based tests — is so important. Knowing your genetic likelihood of developing the condition can raise awareness and motivation to take these vital screening steps.

Predictive Models

Polygenic scores are a relatively new but powerful way to understand a person’s genetic likelihood for a condition. They combine the impact of hundreds or thousands of genetic variants to estimate a person’s chances. Individually, each of these variants only has small effect on a person’s genetic likelihood, but that impact can grow when many variants are considered together.

But the performance these models — which rely on very large genetic studies — tend to perform poorly for Black and African Americans, in part because of the lack of genetic research that includes data from non-European participants.

23andMe wants to improve how its polygenic score for colorectal cancer performs for Black and American individuals and raise awareness about this form of cancer. That is the aim of this newly launched study.

What is Colorectal Cancer?

Cancer occurs when abnormal cells divide and grow out of control. Colorectal cancer occurs in the colon or the rectum, which are sections of the large intestine. This type of cancer usually starts as a growth called polyp.

Most polyps are not cancerous, but some can turn cancerous over time. Left untreated, these cancer cells can spread beyond the colon or rectum through the blood and into the lymphatic system.

Like many forms of cancers, a complex mix of genetics, environment, aging, family history, and lifestyle influence whether someone develops colorectal cancer.

Genes and Environment 

n a few types of colorectal cancer, such as Lynch syndrome, familiar adenomatous polyposis (FAP) and MUTYH-associated polyposis, genetics plays an outsized role. But diets that are low in fiber and fresh fruits and vegetables and high fat and red processed meats contribute to a higher riskier colorectal cancer, as does a lack of exercise, according to the Centers for Disease Control and Prevention. Things like eating a health diet, reducing alcohol consumption, not smoking, and maintaining a health weight can help lower one’s risk for the disease.

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