African-American women with breast cancer were more likely to have larger, later-stage tumors that were more difficult to treat and also had lower survival rates than Hispanic and Caucasian women who received the same treatment in two independent series of clinical trials examined by researchers from The University of Texas M. D. Anderson Cancer Center.
The analysis published on line Oct. 23 by Cancer, a peer-reviewed journal of the American Cancer Society, indicates that race is associated with unfavorable tumor biology, which, along with other factors, likely contributes to the lower rate of breast cancer survival among African-Americans.
"These findings should prompt additional research on how we can improve outcomes for African-American patients by understanding and addressing tumor biology," says first author Wendy Woodward, M.D., Ph.D., assistant professor of radiation oncology at M. D. Anderson. "It's important to identify unique features in different populations and subgroups of all women with breast cancer so we can understand a woman's risk and factors that affect her care on an individual level."
African-American women are less likely than Caucasian women to have breast cancer but are more likely to die from it. Many factors have been implicated in this disparity, the researchers note, including access to health care and screening, differing treatments, socioeconomic status and racial bias.
By examining two series of clinical trials in which treatment was specified and rigorously followed for all patients, the research team minimized biases related to access to care and type of treatment, two variables that often confound analysis of the issue.
Between 1975 and 2000, 2,140 breast cancer patients were treated in two prospective series of clinical trials at M. D. Anderson involving use of the chemotherapy doxorubicin before and after a radical or modified radical mastectomy.
Of the total patients, 1,590 were Caucasian, 300 were Hispanic, and 250 were African-American, with racial categories based on self-reporting by the patients. In both trials, African-American women received at least as many cycles of chemotherapy as did Hispanics and Caucasians.
In the clinical trial for post-operative chemotherapy, the 10-year overall survival rate for African-Americans was 52 percent. For Hispanics and Caucasians it was 62 percent.
More African-American women came to the trial with later stage disease (24 percent compared with 18 percent of Hispanics and 16 percent of Caucasians) and tumors greater than 5 centimeters (22 percent compared with 13 percent each for Hispanic and Caucasians). African-Americans were more likely to have tumors that were estrogen-receptor negative, which are considered more difficult to treat (41 percent compared with 32 percent for Hispanics and 33 percent for Caucasians).
The trial of pre-operative chemotherapy showed similar results, with African-American 10-year survival rate of 40 percent, compared with 56 percent for Hispanics and 54 percent for Caucasians. As in the post-operative trial, higher percentages of African-Americans came to the trial with later-stage disease, larger tumors, and estrogen-receptor negative disease.