SAN ANTONIO--Two poster presentations at the San Antonio Breast Cancer Symposium suggest that breast tumors are more aggressive in African-American women than in Caucasian women.
In the first study, a joint project of the National Cancer Institute (NCI) and George Washington University (GWU), 862 women with breast cancer presenting to the GWU Cancer Center between January 1987 and December 1994 were all staged in the same way and generally went through the same treatment protocols, and yet the African-American women did not do as well in terms of survival as the Caucasian patients.
Survival among patients with stage II/III disease was significantly shorter in the African-American group, and there was a trend toward shorter survival of African-Americans among the stage I patients. An examination of markers for aggressiveness showed that the African-American women were more likely to have a high tumor grade and to be estrogen/progesterone-receptor negative.
"Those were the two most striking factors, but in terms of other assays such as S phase and ploidy, there was also a tendency for the African-American women to have more abnormal values," said Paul H. Levine, MD, of the George Washington University Cancer Center.
The researchers feel that African-American women as a group have more aggressive tumors than Caucasian women and that it is a biologic effect, rather than being due to a delay in diagnosis, Dr. Levine said.
He also believes that heredity is not a major factor in the difference. This conclusion is based in part on studies in Tunisia showing that, over time, the rate of aggressive breast tumors dropped from about 50% initially to about 20%, presumably due to some change in the environment, possibly nutritional.
"Now that we are, I think, documenting biologic differences in the tumors, we're going to look at the risk factors and see why African-American women generally have more aggressive breast tumors than Caucasian women," he said.
In the second study, from the Comprehensive Cancer Center of Wake Forest University, Winston-Salem, NC, no differences in ER/PR status were found between the African-American and Caucasian patients, and, in fact, to date there has been no significant difference in overall survival.
"However," said Vinnette Little, MD, who presented the data, "we did see a trend toward poorer survival in the African-American women as you get out to 10 years of follow-up." In addition, the African-American women had a significantly shorter time to relapse.
A More Select Population
The patients in the Wake Forest study were a more select population than the George Washington University group, Dr. Little pointed out. They were all stage II breast cancer patients who had received the same chemotherapy regimen and had met the same inclusion criteria for the study.
"This may account for the fewer differences seen in our study," she said. "We would have to do further study to see whether there were differences in tumor grade between the two populations, and, if so, that may account for the trend toward poorer survival in the African-American group."