( 930 Canadian women compiled by Charles ...)Study reveals dramatic difference between breast cancers in US and Africa

They found three significant differences:

-- First, breast cancers in African women were more likely to arise from basal-like cells, rather than the inner milk-secreting luminal cells, which are the most common source of breast cancers for U.S. and European women. (This type of basal-like breast cancer is also observed among women with inherited BRCA1 mutations). Tumors that arise from basal cells have a worse prognosis, regardless of race.

-- Second, African breast cancers often lacked estrogen receptors. Although 80 percent of breast cancers in Caucasian women have estrogen receptors, only 23 percent of African tumors did. These tumors do not depend on estrogen and thus will not respond to drugs, such as tamoxifen, that prevent estrogen from reaching the cancer cells.

-- Third, cancers from African women were slightly less likely to express the cell-surface marker HER2. HER2 is the target for the drug Herceptin, which was recently approved for metastatic breast cancer. It is over-expressed in about 23 percent of Caucasians and 19 percent of Africans.

Breast cancer strikes fewer women in Africa, "but it hits earlier and harder," said Olopade. In America, most breast cancer occurs after menopause, usually in the late 50s or 60s. In Africa, it most often strikes women in their 40s. The average age of the African women in this study was 44.

Studies suggest that the rate and genetic profiles of breast cancers in African American women are likely to fall somewhere in between, with a slightly lower lifetime incidence of breast cancer than Caucasians but earlier onset and worse prognosis. African American women under the age of 35 have a 50 percent greater risk of developing breast cancer than Caucasians. This risk levels off by around age 50 and African Americans over 50 have less risk than Caucasians.

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Source:University of Chicago Medical Center