A new study may finally explain why Hispanic women have lower rates of breast cancer than other American women. According to federal data, Latinas have less than a 10 percent lifetime risk of breast cancer, compared with about 13 percent for non-Hispanic whites and 11 percent for blacks.

Researchers at the University of California, San Francisco found that a genetic variant that is particularly common in some Hispanic women with indigenous American ancestry may drastically lower the risk of breast cancer. About one in five American Latinas carry one copy of the variant, and roughly 1 percent carry two.

Health experts once thought that it was behavioral choices that made Latinas less likely to develop breast cancer. Hispanic women tend to have children at a younger age and give birth to more children than non-Hispanic women. They are also less likely to use postmenopausal hormones. All of these factors are associated with a reduced risk for breast cancer. 

But researchers have found that genetics may also play a role. By comparing the DNA of breast tissue in patients of various populations, both with breast cancer and without, the researchers were able to determine that women who carried at least one copy of the genetic variant were about 40 percent less likely to have breast cancer, while those with two copies were 80 percent less likely. The risk was particularly lower for the type of breast cancer known as estrogen-receptor negative, a more aggressive form of the disease.

Now that researchers know that this genetic variant may provide protection against breast cancer, they can use that information to develop better treatments for women who develop the disease.

Related stories about breast cancer on MNN: