New Clues to Race Gap in Breast Cancer Outcomes

July 8 -- TUESDAY, July 7 (HealthDay News) -- The racial gap in breast cancer outcomes, with black women more likely to die from the disease, can't be explained completely by any one factor, new research shows.

For a quarter of a century, researchers have been aware of the so-called race gap in certain cancers. The racial disparity "first emerged about 25 years ago," said Idan Menashe, a postdoctoral fellow at the U.S. National Cancer Institute, who led one of two studies on the topic, both published in the July 15 issue of the Journal of the National Cancer Institute.

Since the mid-1980s, he said, the gap has been widening. "Today is the largest gap we have experienced," he noted.

The two new studies focus on why that may be so, and come to different conclusions. In the first, Menashe and his colleagues compared breast cancer rates for more than 244,000 black and white women, using data from the National Cancer Institute's Surveillance, Epidemiology and End Result (SEER) program.

They looked at the ratios between black and white women when it came to the incidence, mortality and hazard rate -- roughly defined as the probability of dying -- and looked at the tumor's estrogen-receptor status.

Estrogen receptor-negative tumors, or ER-negative, are known to be more aggressive than estrogen receptor-positive tumors, with some experts believing this explained the gap. "What we have shown is, this is not the case," Menashe said.

"We asked what would have happened if black women had the same ER-negative proportion as white women, and we found the mortality disparity would be reduced by only 10 to 20 percent if the proportion of ER-negative tumors were the same in each group," he said.

"We asked what would happen if we equalized the likelihood of dying from the disease. We ruled out that the proportion of ER-negative tumors explains the gap," he said.

They did find that early deaths are driving the disparity between outcomes for white and black women. And, they found that the deaths tend to occur soon after the diagnosis. "Most deaths occur in the two or three years after the diagnosis," he said.