“This difference may be associated with a tumor phenotype that is less responsive to chemotherapy,” said Kathy Baumgartner, epidemiology professor and associate dean for faculty affairs in the School of Public Health and Information Sciences at the University of Louisville. “Increased awareness of this ethnic disparity is needed to improve survival in Hispanic women with breast cancer.”
Breast cancer is the most common cancer and is the second cause of cancer death in women in the United States. Incidence and survival rates vary by ethnicity, and previous research has demonstrated a trend toward poorer survival in Hispanic women.
From 1992 to 1996, Baumgartner and colleagues conducted the New Mexico Women’s Health Study (NMWHS), a statewide, population-based, case-control breast cancer study that examined the difference between Hispanic and non-Hispanic white women for breast cancer risk. In all, 692 women with a first primary breast cancer participated.
In a recent study, the researchers followed the 577 women with invasive breast cancer in the NMWHS through 2008 to assess differences in long-term survival between Hispanic and non-Hispanic white women.
They found that Hispanic women were about 20 percent more likely to die from breast cancer than non-Hispanic white women, which is consistent with other reports, Baumgartner said.
After adjusting for age, stage, lymph node involvement and estrogen receptor (ER) status, the researchers saw the risk drop considerably to almost equal that of non-Hispanic white women — suggesting that “the ethnic difference in breast cancer mortality may be mostly biologically based,” Baumgartner said.
They also found that Hispanic women who received chemotherapy were about 1.5 times more likely to die from breast cancer as were non-Hispanic white women who received chemotherapy, after adjusting for age and the previously noted characteristics.
“It is not clear how much of this ethnic difference in survival is due to socioeconomic factors influencing access to screening and treatment or to biological ones,” Baumgartner said. “Some studies suggest that Hispanic women are more likely to develop ER-negative tumors that are resistant to chemotherapy.”
“Altered response to chemotherapy may partly explain the Hispanic vs. non-Hispanic white disparity in breast cancer survival,” she added.
The study showed no difference between Hispanic and non-Hispanic white women for all-cause or non-breast cancer mortality.
Baumgartner and her colleagues will continue to monitor this cohort for the long term. A grant from the National Cancer Institute and the James Graham Brown Cancer Center supported their research.