CHICAGO – Younger black women who get breast cancer are far more likely than other afflicted women to have a particularly aggressive and lethal form of the disease, a study found.
The findings suggest that biology may help explain why breast cancer is deadlier in black women younger than 55 than it is in white women in the same age group. Other studies have blamed inadequate screening rates.
Since 1990, the average annual breast cancer death rate for younger black women in the United States has been 15.4 deaths per 100,000 population, versus 9.3 per 100,000 for younger white women.
"It's been long known that breast cancer in African American women is a far less common disease than in white women. But when it occurs, it seems to be more aggressive and harder to treat," said study co-author Dr. Lisa Carey of the University of North Carolina's Lineberger Comprehensive Cancer Center.
In the study in Wednesday's Journal of the American Medical Association, researchers identified cancer types by looking for certain proteins in tumor tissue taken from 496 women in the Carolina Breast Cancer Study. The women had been diagnosed between 1993 and 1996.
A quick-spreading form of breast cancer called the basal-like subtype appeared in 39 percent of premenopausal black breast cancer patients. It accounted for 14 percent of breast cancer cases in older black women, and 16 percent of those in non-black women of any age.
Genetic profiling of cancer subtypes has led to a new generation of targeted drugs that have shown startling success. But for the basal-like subtype, no targeted therapies yet exist and doctors must use more conventional chemotherapy.
The research may lead to a better understanding of what causes the aggressive subtype of breast cancer, said Dr. Eric Winer, director of the breast oncology center at Dana-Farber Cancer Institute in Boston. He was not involved in the study.
He said it is unclear whether this subtype is occurring because of an inherited predisposition or because of something in the environment that black women are more likely to be exposed to. He added that disparities in access to treatment still probably account for much of the higher mortality rate among young black women.
In the study, death rates remained higher for younger black women even when the basal-like subtype cases were removed from the data. That suggests that other factors such as access to screening and treatment also play a role in the disparity.
"Biology is only part of the puzzle," Carey said. "Access to health care is very important."
Margaret Rosenzweig of the University of Pittsburgh School of Nursing, who was not involved in the UNC study, said black women may be less likely than white women to follow through on their treatment.
Rosenzweig and her colleagues, in a small study presented in Atlanta last week at the annual meeting of the American Society of Clinical Oncology, showed that poor black women with breast cancer had more difficulty understanding and accepting their treatment than other racial and income groups.
"Clinicians in cancer care need to make a concerted effort to make sure black women understand why they're getting the treatment they're getting and following through with it," Rosenzweig said.