They're commonly referred to as 'triple negatives'--breast cancers that are characterized by three biological components that make the disease more difficult to treat. Oncologists base treatment decisions on the presence of three receptors known to fuel most breast cancers--estrogen receptors, progesterone receptors and human epidermal growth factor receptor 2 or HER2. The most effective agents for breast cancer, such as tamoxifen and trastuzumab (Herceptin), work by targeting these receptors. Women with triple negative tumors lack all three.
In a study of racial differences in the prevalence of triple negative invasive breast tumors, a team of researchers from Emory University's Rollins School of Public Health and Winship Cancer Institute, the Fred Hutchinson Cancer Research Center in Seattle, and the Centers for Disease Control, found the incidence of triple negative disease in African-American women to be more than twice that of white women. "Triple negative disease has not been adequately described or studied, particularly among minority populations," said Emory researcher Mary Jo Lund, PhD. "It has one of the worst prognoses because the tumors have some of the worst characteristics and preclude the use of targeted effective treatments," said Lund.
To assess racial differences in the prevalence of triple negative breast cancer, Lund and her colleagues in Atlanta combined data from their study of racial differences in progression of breast cancer among Atlanta women under the age of 55 with tumor factors analyzed by collaborator Peggy Porter, MD, of the Fred Hutchinson Cancer Research Center
The team found that 47 percent of tumors in black women were 'triple negative' compared to 22 percent in whites. After adjusting for age and stage at diagnosis, black women were almost three-fold more likely than white women to have triple negative tumors.
There also were strong associations found in both black and white women between triple negative disease, high-grade tumors and abnormal expression of p53, a tumor-suppressor gene with cancer-inhibiting properties.
Over all ages, black women are at lower risk for breast cancer compared to white women. However, for women under the age of 50, black women are at increased risk over white women of the same age. "There is also evidence that younger black women have breast tumors with more aggressive features," said Porter.
"Additional studies are needed to examine the molecular profiles and risk profiles for triple negative tumors, and why black women have this increased risk," said Lund. "Our results are provocative and carry the message that African-American women might be at higher risk for worse breast tumors and at an earlier age."