Racal differences in breast cancer survival: Study

By Dr. Ananya Mandal, MDJul 26 2011

Black women are more likely to die from breast cancer than white women with obesity considered a significant factor. But a new study shows that that the cause of the difference does not lie in obesity alone. As a group, black women in the U.S. tend to be heavier than whites and researchers had thought that might explain why only 78 percent survive five years after diagnosis, compared to 90 percent of white women.

Susan M. Gapstur of the American Cancer Society, who wasn't involved in the new work said, “This has been an important question.” Several studies have tied obesity to poorer survival after breast cancer, but only a few small ones have tested whether that relationship varies by race.

The latest study published in the Journal of Clinical Oncology, is the most detailed and well-designed so far, Gapstur said. Yani Lu of City of Hope in Duarte, California, and colleagues used data collected for an earlier breast cancer study on more than 4,500 women living in major American cities. They found that nearly a third of the women were black and the rest were white, and all were between 35 and 64 years old when they were diagnosed with breast cancer. After more than eight years, 14 percent of the white women and a quarter of the black women had died of breast cancer. The women had been interviewed about their weight five years before their cancer diagnosis and more than twice as many black women as white were obese (27 percent versus 12 percent).

End results showed that obese white women had a 46-percent higher chance of dying of breast cancer than their normal-weight white peers and the increased risk remained after taking other diseases and education into account. But there was no such link for blacks. Gapstur said these results would need to be replicated by additional studies in other groups. “It was surprising that this study shows a positive relationship between obesity and breast cancer mortality in white women and not in black women…It raises important questions about other possible reasons.”

Researchers believe differences in tumor biology as well as health care access could be at play. Last year, for instance, one study found that black and Hispanic women wait longer to get drug treatment after breast cancer surgery than whites. Previous research has also found that black women are more likely to be diagnosed with breast cancers at later stages than white women. Gapstur added, “We don't yet have a clear picture… [But] It is always important to maintain a healthy weight, for a variety of reasons.”