Disparities in Breast Cancer Outcomes in African American Women

Key Takeaways:

• Black women with breast cancer have higher mortality rates than White women, which is most likely due to multiple factors including care access, social determinants of health, and differences in phenotype and disease biology.

• Black patients have significantly higher density number per square area of tumor microenvironment of metastases (TMEM) doorways in ER-positive, HER2-negative disease.

• Results of a study that evaluated eight National Surgical Adjuvant Breast and Bowel Project (NSABP) cohorts showed significantly worse outcomes in Black patients with estrogen receptor-positive residual disease, but this was not true for triple-negative disease.

This transcript has been edited for clarity.

Despite incidence being similar in breast cancer between Black [women] and White women, Black women had approximately 40% higher mortality rate than White women, and this is most likely due to social disparity, social determinants of health, such as access to care, and also heterogeneity of the disease, given that Black women have higher incidence of triple-negative disease, which is more aggressive disease than [in] White women.^[1,2,3,4] [Previously], it was thought that this [was] a major contribution [to] disparity.^[5] However, triple-negative disease is less common than ER-positive, HER2-negative disease. ER-positive, HER2-negative disease is the most common breast cancer overall, and it is now known that Black women have a five to six times higher mortality rate in ER-positive, HER2-negative disease compared to White women.^[6] Well, there is no difference in patients who have no racial disparity in mortality rate in triple-negative disease. So, it seems that there are other contributors that play a role in this disparity in outcome, particularly in ER-positive, HER2-negative disease.^[7,8]

One of the components that is being studied now extensively is tumor microenvironment, meaning not only cancer cells but other non-cancer components in the microenvironment, such as vasculature or immune cells, including macrophages. Our team discovered doorways for cancer cell dissemination on blood vessels, which we call tumor microenvironment of metastases (TMEM) doorways.^[9] So, our team recently discovered that compared to White patients, Black patients have significantly higher density number per square area of these TMEM doorways, in particular ER-positive, HER2-negative disease but not in triple-negative disease, and we discovered that that's true for patients who have residual disease after neoadjuvant chemotherapy.

We also recently published a study where we evaluated eight National Surgical Adjuvant Breast and Bowel Project (NSABP) cohorts, and we managed to enrich our study [population with] Black patients and show that Black patients with estrogen receptor-positive residual disease have significantly worse outcome than White patients, but this was not true for triple-negative disease.^[10] I would like to emphasize that our study was very important because we managed to increase the minority percentage in our study from 3% that's usually present in clinical trials to 30% that's actually average for our actual population,^[10,11] and that empowered us to understand the differences in outcome into our microenvironment.

What I would like to end with is that, in addition to eliminating social determinants of health, we have to focus on other factors that may contribute to this 40% higher mortality rate in Black compared to White patients,^[1] and tumor microenvironment would be important to study. In addition, we need to make sure that we increase the participation of Black patients in our trials.^[12]