Survival after breast cancer has improved dramatically over the past few decades. Earlier detection and better treatments mean that many women now live for years, and often decades, after diagnosis. But these gains have not been shared equally. In the United States, Black women still face a higher risk of dying after a breast cancer diagnosis than White women. At the same time, cardiovascular disease has emerged as one of the leading causes of death among breast cancer survivors. Together, these trends raise an important question: when survival differs between racial groups after breast cancer, how much of that difference comes from the cancer itself, and how much from heart disease?
A recent study published in Cardio-oncology, led by Dr. Kerryn Reding of Fred Hutch Cancer Center and colleagues, approached this question using data from the Women’s Health Initiative (WHI), one of the largest and longest-running studies of women’s health in the United States. “This study makes a significant contribution by disentangling the relative contributions of cancer-specific mortality and cardiovascular mortality,” Dr. Reding explained. “Despite Black women having more cardiovascular disease than White women, our results showed that mortality due to breast cancer was the primary driver of racial disparities in survival after breast cancer.”
The study included women who were diagnosed with invasive breast cancer during their participation in the WHI. Researchers focused on three outcomes in the ten years after diagnosis: nonfatal cardiovascular events, deaths caused by cardiovascular disease, and deaths caused by breast cancer. Analyzing cause-specific mortality after cancer is complex because different health risks unfold simultaneously. A patient who dies from breast cancer, for example, cannot later experience cardiovascular death. To account for this, the investigators used statistical approaches designed to evaluate “competing risks,” which estimate the chance of dying from one cause while accounting for the possibility that another cause occurs first.
The results showed that Black women in the cohort experienced more cardiovascular events after their cancer diagnosis than White women. Within ten years of diagnosis, about 11% of Black women had experienced a cardiovascular event compared with 8% of White women. At the same time, disparities in breast cancer mortality were evident. Ten years after diagnosis, the cumulative incidence of death from breast cancer was 15% among Black women compared with 11.5% among White women. Even after researchers accounted for differences in health conditions, tumor characteristics, and lifestyle factors, Black women remained significantly more likely to die from breast cancer. When the researchers examined cardiovascular mortality, however, the pattern appeared to reverse. White women had a higher cumulative incidence of cardiovascular death over the same period—about 10% compared with 7% among Black women. At first glance, this finding seems counterintuitive, given the higher burden of cardiovascular events among Black women.
Dr. Reding said the explanation lies in how these risks unfold over time. “Breast cancer deaths may mask the underlying cardiovascular vulnerability in Black women because there is a shorter timeframe to breast cancer death than cardiovascular death,” she said. If breast cancer survival were equal between groups, cardiovascular disparities might become more visible. The study also provides context for why breast cancer mortality remains higher among Black women. In this cohort, Black participants were more likely to be diagnosed with advanced disease and with triple-negative breast cancer, a more aggressive subtype characterized by the absence of estrogen, progesterone, and HER2 receptors, which is harder to treat. They were also more likely to have higher body mass index, diabetes, and hypertension. These differences reflect a combination of factors influencing biological pathways and broader structural influences, including access to care and longstanding inequities in the healthcare system.
“These findings raise important questions about how cardiovascular disparities may emerge or worsen if breast cancer mortality improves and more Black women live long enough to experience cardiovascular disease,” Dr. Reding said. Understanding those risks, she added, will require further research into the mechanisms behind cardiovascular vulnerability after cancer, including treatment-related cardiotoxicity and differences in access to guideline-concordant cardiovascular care.
Ultimately, the study highlights a broader challenge in cancer survivorship research. Focusing on cancer outcomes alone may obscure other health risks that shape long-term survival. As Dr. Reding noted, “this work calls out the need to confront upstream determinants that shape these inequitable health outcomes so that both cancer and cardiovascular disease can be addressed in these women.”
This study was supported by the Women’s Health Initiative (WHI) program, National Heart, Lung, and Blood Institute, National Institutes of Health, U.S. Department of Health and Human Services.
Fred Hutch/University of Washington/Seattle Children’s Cancer Consortium Member Dr. Kerryn Reding contributed to this research.
Reding, K. W., L Vasbinder, A., Cheng, R. K., Barac, A., Wang, Y., Szewczyk, W. J., Haque, R., Ballinger, T. J., Breathett, K., Shadyab, A. H., Shih, R., Nuno, T., Wild, R. A., Zhang, X., Nassir, R., Mouton, C., Lane, D. S., Martin, L. W., Manson, J. E., (2025). Racial differences in breast cancer-specific mortality and CVD-specific mortality after breast cancer in post-menopausal women. Cardio-oncology (London, England), 11(1), 112.
Science Spotlight writer Darya Moosavi is a postdoctoral research fellow within Johanna Lampe's research group at Fred Hutch. Darya studies the nuanced connections between diet, gut epithelium, and gut microbiome in relation to colorectal cancer using high-dimensional approaches.
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