A large analysis of racial differences in rates of estrogen receptor (ER)-negative breast cancer finds that black women in the United States are more likely than white women to have breast tumors that are ER-negative, researchers from the University of Michigan Comprehensive Cancer Center report.
ER-negative tumors are associated with less favorable outcomes than those that are ER-positive, in part because anti-estrogen therapies—effective with ER-positive tumors—do not affect ER-negative tumors.
The overall incidence of breast cancer in black women is lower than in white women, but survival rates are significantly lower in black women than in their white counterparts. Black women have a higher incidence of breast cancer at younger ages and also are diagnosed at later stages of disease. Much of this discrepancy has been attributed to socioeconomic factors such as access to screening and adequate cancer care. But this study suggests that there is also a biological basis for differences in survival rates.
The investigators analyzed data on 170,079 cases of breast cancer included in the National Cancer Data Base (NCDB), a multi-institutional tumor registry that collects cancer data from 1,600 hospitals in all 50 states. White women comprised 90.3 percent of cases; black women accounted for 9.7 percent of cases. For women with invasive cancers, ER-negative tumors were significantly more frequent in black women at every stage of disease and in all age categories: 39 percent of black women had ER-negative tumors, compared with 22 percent of white women.
The data also showed that black women were diagnosed at a younger average age (57 for black women vs. 62 for white women) and at a later stage (29 percent were stage 1 vs. 42 percent for white women). They also had larger tumors at diagnosis and cells that were more poorly differentiated, which is associated with less favorable outcomes.
“Differences in tumor biology have a significant impact on survival,” said M. Catherine Lee, M.D., a clinical lecturer in the department of surgery at the University of Michigan Comprehensive Cancer Center and the study’s lead author. “The fact that breast cancers in black women are more aggressive biologically suggests that we need to focus more of our research energy on developing better treatments targeting ER-negative tumors. These findings also point to a need for improved cancer education and screening in black women, particularly those in younger age groups.”
Lee presented the study results at the 2007 Breast Cancer Symposium, co-sponsored by the American Society of Breast Disease, the American Society of Breast Surgeons, the American Society of Clinical Oncology, the American Society for Therapeutic Radiology and Oncology, the National Consortium of Breast Centers, and the Society of Surgical Oncology Sept. 7-8, 2007.
It is estimated that more than 180,000 new cases of breast cancer will be diagnosed in the United States in 2007, and more than 40,000 people will die from the disease.
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