|Racial Disparities in Breast Cancer Mortality are Not Driven by Estrogen Receptor Status Alone|
This study identifies factors for differences in rates of breast cancer in black vs. white women that heretofore have been uncertain.
Akinso: Black women who are diagnosed with breast cancer have a higher probability of dying from the disease than white women.
Menashe: We know that in the last 20 years breast cancer mortality rates are higher in black women than in white women.
Akinso: Dr. Idan Menashe is the lead author of the study and research fellow at in the National Cancer Institute's Division of Cancer and Epidemiology and Genetics.
Menashe: Two major factors having suggested to contribute to this racial disparity. The first one is differences in access to care. The second factor is the biological differences between these two populations.
Akinso: In this study researchers compared breast cancer rates for black and white women using data from the NCI's Surveillance, Epidemiology and End Result program. They used statistical techniques to directly evaluate racial disparities in breast cancer outcomes by examining the rate ratios between black and white women for incidence, morality and hazard rate, as well as performing sub-comparisons by estrogen receptor negative status. Dr. Menashe explains why black women could be at a high risk for breast cancer.
Menashe: We know that black women tend to have higher prevalence of the estrogen receptor negative, or we call it ER negative, tumors which are the more aggressive and more difficult to treat tumors. And therefore people suggest that these differences could account for this racial gap.
Akinso: Researchers found that, from 1990 to 2004, incidence rate ratios remained fairly stable while the breast cancer mortality rate ratios persistently increased. Furthermore, the researchers observed that, regardless of estrogen receptor status, black women with breast cancer were still more likely to die of the disease than white women. Dr. Menashe says because of the data they were able to pinpoint that disparate outcomes between black and white women, particularly in the first few years following breast cancer diagnosis, are the driving factor behind the racial gap.
Menashe: The goal of our study was to explore the underlying causes of the black/white racial disparity in breast cancer mortality in the U.S. We employed different statistical analysis, but particularly we used a statistical approach called an incidence based mortality that allows us to examine the mortality rate according to specific tumor characteristics, for example the differences in ER status.
Akinso: This disparity remained even when the researchers adjusted for age at diagnosis, stage and grade of the tumor, year of diagnosis, and socioeconomic status. When the researchers examined hazard rate trends in black and white women, they noticed that the largest differences occurred in the first three years after diagnosis in both estrogen receptor negative and positive tumors. Dr. Menashe examines the findings.
Menashe: Our construction analyses reveal that the higher prevalence of ER- tumors among black women explain only a small portion of the black/white mortality gap. In contrast, we found out that differences in breast cancer outcome, especially in the first few years following the diagnosis, account for the majority of the disparity. In our analysis we showed that within the first five years after breast cancer diagnosis, black women are twice more likely to die of this disease than white women irrespective of their tumor characteristics.
Akinso: Dr. Menashe hopes that clinicians and other researchers can use the findings to uncover, address, and eliminate the factors for poorer early outcomes for black women. For more information, visit www.cancer.gov . This is Wally Akinso at the National Institutes of Health Bethesda, Maryland.