Breaking Down Breast Cancer Disparities

In the 1970s, before the widespread use of mammography as a screening tool, Black and White women had similar breast cancer mortality rates. Back then, breast cancer was detected by the appearance of symptoms, and with chemotherapy still in its infancy, treatment for many patients consisted of radical mastectomy. 

Throughout the 1980s — and persisting until today — the death rate in Black women began to exceed that seen in White women, due to the unequal dissemination of mammography screening and new treatments. In October, the American Cancer Society (ACS) released its biennial update of breast cancer statistics among women in the United States, finding that this racial disparity has mostly widened over the past four decades. 

The results show that Black women have lower survival rates than women of every other racial and ethnic group for every breast cancer subtype and stage of diagnosis, except localized-stage disease. 

Adana Llanos, PhD, MPH, associate professor of epidemiology at the Mailman School of Public Health at Columbia and co-leader of the Cancer Population Science Program of the Herbert Irving Comprehensive Cancer Center (HICCC), studies the molecular and sociobiologic mechanisms that underlie cancer inequities.

Below, Dr. Llanos discusses the distinction between cancer inequities and disparities, the latest findings from the ACS report, and how the gap between Black and White women can be addressed.

First, what is the difference between cancer disparities and cancer inequities? Are the terms interchangeable? 

When I give talks, I usually pause and say what I mean by a health disparity and a health inequity, because they are different. A health disparity describes a difference between populations, whether that be the incidence, prevalence, mortality, or just an overall difference in the disease burden. It's simply a difference in the data point that you're looking at. On the other hand, inequities are differences in these data points or health outcomes of interest that are the result of systemic, structural, and unjust factors. 

What does the new ACS study of breast cancer statistics tell us about disparities between Black and White women today? 

The ACS report found that the breast cancer mortality rate has dropped by 44% since 1989 — which is great, but the data show that not all populations have benefited equally. Compared with a 43% reduction in the breast cancer death rate among White women since 1990, decreases were only around 30% among Hispanic and Black women. I think it's problematic that we're not seeing the same reduction in breast cancer mortality across all groups. So my question is, is that progress? 

Black women are at least 40% more likely to die of breast cancer than White women, despite having similar incidence rates, which is a disparity — but I would say it's also an inequity. The more we study the explanations for this disparity, I feel that it's pretty safe to say that the difference in mortality rates isn't due to some genetic difference between Black and White women. In fact, it's more likely due by upstream factors like structural racism, neighborhood characteristics, and access to optimal, equitable health care. 

For example, Black women are less likely to receive state-of-the-art, high-quality screening, and there are issues around follow-up after screening. Delayed care is definitely something that we see in Black women, and the longer you delay care after being diagnosed, the less likely the tumor is going to be amenable to treatment. 

How can these cancer inequities be remedied? 

There are lots of questions that we still need to answer about how advancements in medicine generally and treatment for breast cancer specifically may be exacerbating inequities. One thing to consider is the lack of representation of Black and African ancestry populations in the cancer genomics research that might lead to precision therapeutics. We don't really know that much about the genetic variants observed in these populations, and that's because they've been excluded from this type of research. 

Another example is that Black women represent 3% of the participants in randomized control trials for breast cancer therapeutics, but they represent 12% of breast cancer patients. That is a severe underrepresentation in these studies that ultimately lead to FDA approvals for these drugs. 

I recently served on the steering committee of the recently released AACR 2024 Cancer Progress Report, and all together, we're making progress in the fight against cancer but the progress is unequal across populations. So, we still have such a long way to go, especially when it comes to figuring out the best ways to address inequities and improve cancer outcomes for everyone.