Blacks less likely to survive advanced breast cancer regardless of radiation therapy
More study needed to determine cause for racial disparity
UC Davis researchers have found that blacks are more likely than patients from other racial and ethnic groups to die from advanced breast cancer and that the disparity cannot be explained by the fact that blacks are less likely to receive radiation therapy, a standard treatment for advanced disease.
“We knew from our earlier study that blacks with advanced breast cancer were less likely to be treated with radiation, so we expected to see that their survival would be poorer because of that,” said Steve R. Martinez, principal investigator of the study and assistant professor of surgical oncology at UC Davis Cancer Center. “We were surprised to find that blacks fare worse regardless of whether they receive radiation therapy and actually appear to be less responsive to one of our most important treatments.”
The study, published online in the journal Cancer, evaluated data from more than 12,000 patients in the Surveillance, Epidemiology and End Results database with advanced breast cancer between 1988 to 2005. The data allowed analysis of patients by racial and ethnic group, types and characteristics of breast cancer, type of surgery and whether or not they received radiation therapy. Death rates from breast cancer and other causes were determined.
A previous study from Martinez’s research group showed that blacks are not as likely as whites and Asians to receive radiation therapy following breast cancer surgery. According to the current study, however, blacks had death rates more than 50 percent higher than those of patients from other racial and ethnic groups regardless of whether they received radiation therapy. This indicates that lack of radiation therapy was not a factor in the higher death rates and raises questions regarding the actual causes the poorer survival.
Although in their previous study, Hispanic patients, like blacks, were found to be less likely to receive radiation therapy, this study showed that their survival rates were similar to those of whites and Asians. The reason Hispanics actually did better than expected also is unknown.
In general, radiation therapy is recommended for all patients with breast cancer who undergo lumpectomy (removal of only the tumor and the surrounding tissue) as well as for those who have mastectomy (complete breast removal) if the tumor is large or at least four lymph nodes are also found to be cancerous. Such patients with advanced breast cancer typically also are treated with hormonal or chemotherapy before or after surgery.
“Why blacks fare worse from breast cancer is the million-dollar question,” said Martinez. “This study is significant in the questions it raises, and looking for the answers is critical as we go forward.”
According to Martinez, one explanation for the disparity may be that blacks have a biologically different form of breast cancer that is more aggressive and less responsive to radiation and other therapies. Blacks also may be more often predisposed to life-threatening complications of radiation therapy such as stroke, cardiac disease and lung damage.
It has also been shown in other studies that blacks are less likely than whites to receive chemotherapy or hormonal therapy, which could account for the higher death rates. Martinez intends to explore this possibility. Unfortunately, said Martinez, information about the use of hormonal and chemotherapy is not as accessible from current databases as information about radiation therapy. Because there are many causes of health-care disparities, studying and better understanding them are crucial to improve the care provided to all patients, Martinez explained.
“Disparities may be due to poor access to care, in which case research in these areas can help focus health-care dollars to target particular populations in need,” he said. “Disparities in cancer survival may also be the result of differential tumor biology among populations. Identifying these biological differences may help us find more specific, individualized and targeted therapies for treatment.”
In addition to Martinez, other authors of the study “Do radiation use disparities influence survival in patients with advanced breast cancer?” were Warren H. Tseng, Robert J. Canter, Allen M. Chen, and Richard J. Bold, all of UC Davis. Another author, Steven L. Chen, previously chief of breast surgery at UC Davis, is now with City of Hope in Duarte, Calif.
The research was supported by a grant from the National Center for Research Resources, a component of the National Institutes of Health and NIH Roadmap for Medical Research.