Women of African descent are more likely than whites to suffer an earlier and more virulent form of breast cancer, and doctors need to re-evaluate how black women are diagnosed and treated, a study said Monday.

“The discovery means we have to rethink how soon and how often we screen for breast cancer in women at risk for the most aggressive type of breast cancer, as well as how we prevent it and how we treat it,” said Funmi Olopade of the University of Chicago.

Current guidelines “were developed based on our deep knowledge of breast cancer in older women of European ancestry, but our results mean that much of the U.S. and European data simply do not apply to the types of breast cancer we most commonly see in African women” or those of African descent, she added.

The finding, based on a comparison of breast cancers in Nigeria, Senegal and North America, was released in California at a meeting of the American Association for Cancer Research.

The study found an earlier and different form of breast cancer afflicted women living in Africa. While black women in North America had a lower risk of breast cancer than whites in general, their ancestry still put them at a higher risk for the cancers seen in Africa, it added.

“We need to reconsider how to screen for a disease (in blacks) that is less common but starts sooner and moves faster. Obviously an annual mammogram beginning at 50 is not the best route to early detection in African women, who get the disease and die from it in their 40s, and it also needs to be adjusted in African Americans” who had a slightly lower level of risk because of racial mixing, she added.

U.S. black women under the age of 35 had a 50 percent greater risk of developing breast cancer than whites but the risk leveled off by about age 50, after which the risk was lower than for whites, the study said.

‘CLEAR EVIDENCE’

Olopade said it was thought for some time breast cancer was somehow different in Africa, “but there was no real sense of how much of that was biology and how much was environment.”

“Now we have clear evidence that nature plays an important role. These tumors are biologically quite different in ways that make this a worse disease,” she added.

The report found tumors in 378 Africans were more likely to originate from a different group of cells within the breast. As a result, they are not the same molecular targets that form the basis of many standard therapies, said Olopade, who heads the school’s Center for Clinical Cancer Genetics.

When comparing the African tumors with tissue samples from 930 Canadian women in a database in British Columbia, the researchers found the former were more likely to arise from basal-like cells, rather than the inner milk-secreting cells, which are the most common source of breast cancers for North American and European women.

Tumors that started in basal cells had a worse prognosis, regardless of race, the report said.

In addition, tumors seen in the African women do not depend on estrogen and as a result will not respond to drugs, such as tamoxifen, that prevent estrogen from reaching the cancer cells.