BETHESDA, MD—Black women die from breast cancer at a higher rate than white women, but exactly why remains unclear. A new study from the Military Health System just shot down one of the leading explanations for the disparity.
One suggested reason for differences in outcomes is that black women tend to have longer delays between breast cancer diagnosis and surgery, often as a result of insurance issues and access to care in the general population.
Even within the Military Health System, which eliminates access and coverage issues, non-Hispanic black women experience a longer wait between diagnosis and surgery than non-Hispanic white women, according to an analysis conducted by researchers at the John P. Murtha Cancer Center, Uniformed Services University and Walter Reed National Military Medical Center in Bethesda, Maryland.
The delays did not explain the racial disparity in overall survival among women who had breast-conserving surgery, however.
The retrospective study, which appeared in JAMA Surgery, analyzed differences in time to surgery and outcomes between 998 non-Hispanic black women and 3,899 non-Hispanic white women in the DoD Cancer Registry and Military Health System Data Repository who had Stage I to Stage III breast cancer. The women had either mastectomies or breast-conserving surgery in the MHS between January 1998 and December 2008.
Median time to surgery was similar between the two groups of women, 21 days for white women and 22 days for black women. At the upper percentile ranges, however, greater delays appeared for black women who had an additional 3.6 days of waiting at the 75th percentile and nearly 9 more days of delay at the 90th percentile. The choice of surgery did not have a significant impact on the differences in delays.
Multivariate analyses that excluded time to surgery found that black women had a 45% higher risk of death than white women who had breast-conserving surgery, though there was no significant difference in outcomes between black and white women who had mastectomies. When the researchers factored in time to surgery, the disparity in outcomes remained similar. Black women had a 47% increase in mortality risk compared to white women who had breast-conserving surgery. Again, no difference in mortality risk was detected for women who received mastectomies.
Nearly two-thirds of the women in both groups had mastectomies and just over one-third had breast-conserving surgery. “There were no significant racial differences in type of surgery received,” said co-author Kangmin Zhu, MD, PhD.
“This study’s results indicate that time to breast cancer surgery was delayed for non-Hispanic black compared with non-Hispanic white women in the Military Health System. However, the racial differences in time to surgery did not explain the observed racial differences in overall survival among women who received breast-conserving surgery,” the authors said.
Because black women in the study were more likely to have hormone-receptor negative breast cancer (31.1% vs 19%), the research team explored whether this status contributed to the longer delays in the 75th and 90th percentiles.
“It is well-known that HR-negative tumors are more aggressive than HR-positive tumors. Thus, the former may require more aggressive treatment and possibly neoadjuvant chemotherapy,” Zhu told U.S. Medicine. “The implementation of more aggressive treatment(s) result from the patient’s culture and attitude, doctor-patient interaction, family support and others. Thus, the necessary time for treatment planning or neoadjuvant treatment may result in different length of time to surgery.”
Among patients receiving adjuvant treatment, black women had longer time between surgery and adjuvant chemotherapy than white women, but the analysis did not find that the longer time affected the risk of all-cause death.
Multivariable analysis found that hormone receptor status also did not explain the disparities in time to surgery, however, leading the authors to suggest that “other factors, such as genetic or familial risk; social, behavioral, and cultural factors; and patient attitudes and perceptions not routinely captured” may contribute to these differences.
While the researchers did not focus their analysis on racial differences in tumor stage or differences in patient characteristics, crude data indicated that some of those factors might contribute to the poorer outcomes for black women with breast cancer in the study.
The median age at diagnosis was 52 years for white women and 46 years for black women. Black women were diagnosed with breast cancer before the age of 40 at twice the rate of white women, 25% vs. 13%. Just over one-third of black women were diagnosed after age 50, while 57% of white women were in this older age group.
Not only were the black women typically younger, they were more likely to have more advanced cancer at diagnosis. Almost half of white women (49.3%) had Stage I cancer at diagnosis compared to 37.4% of black women, while 15.8% of black women were Stage III at diagnosis vs. 10.6% of white women.
“Young women and women with more aggressive phenotypes (e.g., triple-negative breast cancer) tend to have later stage of cancer” at diagnosis, Zhu said.
The findings of earlier and more-advanced cancer in black women in the MHS support results seen in other studies and has led some organizations to advocate screening black women for breast cancer at younger ages.
Last year, the American College of Radiology and the Society of Breast Imaging changed their guidelines to classify black women as “high risk” for breast cancer. The organizations recommend initial screening at age 30, “so that those at higher risk can be identified and can benefit from supplemental screening.”
They based their recommendation on the higher incidence of breast cancer in black women under the age of 45 and the higher rate of BRCA1 and BRCA2 mutations. Other significant factors included the high rate of aggressive triple-negative breast cancers among black women, which is twice the rate seen in white women, and the 42% increase in mortality risk for black women with breast cancer.
Zhu noted that “our study focused on the time interval between diagnosis and surgical treatment, which is not directly related to cancer screening that occurs before diagnosis. Therefore, we cannot extend our findings to whether black women should have earlier or more frequent screening for breast cancer.”