Race, Genetics & Cancer

What role does race and ethnicity play in cancer?

At age 35, Carey Weiner was about to get tested to see whether she had a form of a gene that would put her at greater risk for breast cancer. But before Weiner, of Wellington, Florida, could get the test, she found out the risk was a reality: she had ductal carcinoma in situ—cancer contained within the ducts of the breast. Weiner, who is of Ashkenazi Jewish descent, had known her risk could be high. Her maternal grandmother died from breast cancer, and her mother and aunt tested positive for the genetic variant—a mutation in a gene called BRCA1. But Weiner’s gynecologist told her, in error, that she was too young to worry about it.

In September 2007, Weiner underwent a bilateral mastectomy and learned that she, too, had the BRCA1 mutation. In 2008, she had a total hysterectomy, including removal of her ovaries, to protect herself from another threat posed by BRCA1: ovarian cancer.

Genetic mutations linked to specific cancers can affect certain racial or ethnic groups more than others. For instance, the same BRCA1 mutation, which is more common in Ashkenazi Jews than in the population as a whole, also appears to be somewhat more common in Latinas. Meanwhile, mutations in another breast cancer-related gene, BRCA2, are slightly more frequent among African-Americans, putting them at higher risk of very aggressive breast and ovarian cancers compared with white women, according to the National Cancer Institute. (Women of any racial or ethnic group with a family history of breast cancer, or with relatives known to have mutations in the BRCA1 or BRCA2 genes, should discuss the possibility of testing with a genetic counselor.)

For African-American men, several genetic factors tied to prostate cancer have been reported, the NCI says. Specifically,­ recent research has found different combinations of genetic variants associated with higher or lower prostate cancer risk—and the bulk of those linked to higher risk were found most often in African-Americans.

Another example involves Asians. Recent evidence suggests a particular genetic variant, which affects alcohol metabolism, increases liver cancer risk, and that this variant is most common in people living in southeast China.

Other discoveries relate to how the body metabolizes drugs or other substances that can affect the vitality of a tumor.

“Genetic factors can impact how a tumor progresses and how it will react to various treatments,” says Sanya Springfield, PhD, director of the NCI’s Center to Reduce Cancer Health Disparities. “Some ethnic groups may experience greater toxicity when treated with the same dose and schedule of drugs. In other words, based on your genetic differences, a person may react differently to different drugs. This is because of gene variations in drug-metabolizing enzymes.” 

For instance, a variant of a gene called CYP2D6, found more often in Asians, may result in poor metabolism of the breast cancer treatment tamoxifen. Because the drug is not converted to its more active form, the medicine could be rendered less effective and other treatments might be better choices.

Research is also beginning to sort out how race or ethnicity is linked to biological differences in tumors themselves.

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