A genetic trait protects many women of Latin American descent from breast cancer, researchers probing the ethnic biology of cancer said Monday.

If confirmed, the finding may lead to more effective genetic testing for women at risk, by helping to determine who most needs to take preventative measures. Breast cancer is the most common cause of cancer among women.

Generally, fewer Hispanic women develop breast cancer and fewer of them die from it, compared with women of European or African-American ancestry, medical statistics show. On Monday, an international team led by researchers at the University of California, San Francisco, said they now know why.

A single difference in just one of the three billion letters of biochemical DNA code in the human genome makes Latinas who inherit it about 40 percent less likely to develop breast cancer, medical geneticist Laura Fejerman and her colleagues reported Monday in Nature Communications.

If women have inherited the variation from both sides of their family, they are 80 percent less likely to get breast cancer.

“It is strongly protective,” said cancer specialist Elad Ziv at the UCSF Helen Diller Family Comprehensive Cancer Center, who helped conduct the study funded by the National Cancer Institute. “We really need to do more experiments to nail it down and understand what it is doing.”

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