We recently published our finding from an investigation of ongoing racial disparities from breast cancer (J Cancer 2020; doi: 10.7150/jca.39091). We noted that, while breast cancer mortality rates have been declining over the past 30 years, disparities in death rates between African-American and Caucasian women have not decreased. In fact, they have increased, according to some reports.
We noted that these disparities had been attributed to a cadre of well-documented social-, screening-, patient-, disease-, and treatment-related factors, all well known to the oncology community. However, while overall differences in survival have not narrowed, we pointed to some data in published reports, which were neither discussed nor analyzed in the publications, denoting an opposite effect.
The data suggested that there may be subpopulations of African-American women with specific categories of breast cancer whose survival may have improved more than that of Caucasian patients in the past decades. This prompted us to compare systematically changes in survival differences over time between stratified subpopulations of African-American women with breast cancer to their corresponding categories of Caucasian women.
Approach to Looking for Bright Spots
Our study analyzed the Surveillance, Epidemiology, and End Results (SEER) database to compare differences in survival between African-American and Caucasian women between the decades saddling the turn of the century while controlling for tumor and patient characteristics.
Our report analyzed 395,170 patients with breast adenocarcinoma from 1990 to 2011 who had a recorded race, age, stage, grade, ER and PR status, marital status, and laterality as control. We grouped patients into two time periods, 1990-2000 and 2001-2011; three age categories: under 40, 40-69, and >70 years; and two stage categories: I-III and IV. Our study used the Kaplan-Meier and log-rank tests to compare survival curves. The publication stratified data by patient- and tumor-associated variables to determine co-variation among confounding factors. We used the Pearson Chi-square test and Cox proportional hazards regression to determine hazard ratios to compare survival.
Our findings showed that both Caucasian and African-American patients with stage I-III and stage IV breast cancer had significantly lower Cox hazard ratios in the 2001-2011 time period than in the 1990-2000 time period, with a few exceptions in some of the stratified categories. Overall, differences between African-American and Caucasian survival curves persisted, and population-averaged data did not show differences between rates of improvement between the two groups, in agreement with the published literature.
After stratifying the data, however, our results demonstrated a clear and significantly greater improvement in survival in African-American women with ER- (Cox HR 0.70 [95% CI 0.65-0.76]) and PR- (Cox HR 0.67 [95% CI 0.62-0.72]) stage I-III breast cancer in 2001-2011 than in Caucasian women with ER- (Cox HR 0.81 [95% CI 0.78-0.84]) and PR- disease (Cox HR 0.75 [95% CI 0.73-0.78]). This improvement in survival in African-American women was not associated with changes in the distribution of tumor or patient attributes.
We further stratified patients with ER- and PR- stage I-III tumors to additional patient- and tumor-associated variables. The results then showed that African-American women with ER- cancer who had stage I tumors, PR- tumors, or were married had greater improvement in survival than Caucasian women in the same categories. Similarly, African-American women with PR- tumors who were >70 years old, had stage I cancer, had ER- tumors, or were married had greater improvement in survival than their Caucasian counterparts.
The study also revealed that some subgroups of patients with stage I-III disease had less improvement in survival than other patients in their respective stratification categories. This included ER- and PR- Caucasian patients compared to ER+ and PR+ Caucasian patients, Caucasian and African-American patients >70 years old compared to their respective younger subgroups, and widowed African-American patients compared to single or married African-American patients.
Implications & the Path Forward
Our study was the first to report an improvement in racial disparities in survival in a subset of breast cancer patients. Because further stratification of the ER- and PR- patients by tumor- and patient-associated variables did not support a role for these co-variables in our findings, we proposed that perhaps treatment-associated variables might have played a role.
ER-/PR- Caucasian patients improved less in the decade after the century than ER+/PR+ Caucasian patients. This suggested that a relative lack of progress in effective novel therapies for hormone receptor-negative breast cancer resulted in a limit to improving survival with available treatments.
In the manuscript, we pointed out that the data suggest that perhaps African-American patients are catching up to these limits due to a general improvement in the rate of standard treatment for localized breast cancer. A greater national focus on awareness in disparities in the treatment of and clinical trial participation by African Americans through programmatic efforts may have also raised the general awareness to provide appropriate treatment and cancer control.
We concluded that we might not, therefore, be witnessing an improved survival in appropriately treated patients. Instead, we may be seeing the effects of an increase in the fraction of African-American women receiving standard treatment.
The implication that the rate of administering standard-of-care treatment for breast cancer to African-American women has started to improve is a small step, albeit a significant one. Much has been written and communicated about the immense disparities in all breast cancer areas, including prevention, detection, diagnosis, treatment, clinical trial participation, follow-up, and survival care. Yet, African-American women lag in all of these areas. Efforts by the National Cancer Institute, governments at all levels, foundations, non-government groups, and academic institutions remain ongoing. Still, we must do much more to close the remaining gap in disparate survival from this disease.
ROBERT WIEDER, MD, PHD, is Professor of Medicine in the Division of Oncology/Hematology at Rutgers New Jersey Medical School and Member at Rutgers Cancer Institute of a New Jersey. BASIT SHAFIQ, PHD, is an Adjunct Assistant Professor at Rutgers University–Newark. NABIL ADAM, PHD, is a Distinguished Professor with Rutgers University–Newark and Department of Medicine, Rutgers New Jersey Medical School.
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