New Insights into the Links Between Heart Disease and Breast Cancer
For Heart Health Month, Amy Ahnert, MD, discussed the link between cardiovascular disease and breast cancer.
Scientists and physicians have long been aware of links between cardiovascular disease (CVD) and breast cancer. Both conditions share common lifestyle risk factors, such as smoking, obesity, physical inactivity, and poor diet. Additionally, chemotherapy for breast cancer may increase the risk of developing chemotherapy-induced heart disease, known as cardiotoxicity.
A new study published Jan. 2 in JAMA Network Open points to a causal relationship between the two diseases.1
The population-based study of more than 19,000 older (median age 73) invasive breast cancer patients found that those with advanced breast cancer at the time of diagnosis had a 10% increased chance of prevalent CVD by comparison with matched patients with early-stage breast cancer.
The study therefore suggests that patients with CVD are at increased risk of advanced breast cancer at diagnosis.
Though the new research found a correlation between CVD and advanced breast cancer, it did not establish causality, which will require further studies. Distinguishing correlation from causality is a significant challenge in biomedical research. To illustrate this, scientists often use the fire truck analogy: the presence of fire trucks at 100% of house fires (correlation) does not imply that the fire trucks caused the fires.
Still, the identification of the correlation raises an intriguing signal that a causal relationship may exist, especially in light of previous research showing that CVD may play a direct causal role in the etiology and progression of cancer. The previous studies, which demonstrated that tumor growth is accelerated in the context of heart failure, cardiac remodeling and myocardial infarction, suggest a direct causal link, perhaps due to immunosuppression.
Yet, the question remains – What should be done in response to these findings?
Breast Cancer: © SciePro - stock.adobe.com
Need for Education and Awareness
First and foremost is the need for more education and awareness.
This study is a stark reminder that CVD—not breast cancer—is the leading cause of deathamong women in the US and worldwide.2 In 2021, it accounted for one in five female deaths (310,661 women), while over 60 million US women live with heart disease. By comparison, breast cancer claimed an estimated 42,250 lives in 2024—less than a seventh of CVD deaths. 3
Despite these concerning statistics, only 56% of women in the U.S. identify CVD as the leading cause of death among females. Cardiac literacy is needed now more than ever. Heart attack hospitalization rates among women under 55 are increasing, while rates among men the same age have dropped.4 Women are also more likely to die from a heart attack. And they continue to be undertreated for CVD by comparison with men.
The study also underscores the importance of regular screenings for CVD, as well as for breast cancer. If, as the study shows, CVD is a risk factor for advanced breast cancer, then cardiovascular screening and treatment can not only improve CVD outcomes, but breast cancer outcomes as well.5
Beyond the Bikini
In addition to highlighting the need for more research at the interface of heart disease and breast cancer, a field known as cardio-oncology, the study also points up the need for more gender-specific cardiology research in general. For years, CVD was thought to be a “man’s disease.”4 Concerns about women’s health were said to be limited to the parts of the female body “under the bikini.” Because CVD was thought to be a man’s disease, research participants were primarily men. Though data from trials consisting primarily of men have historically been applied to women, women aren’t just small men.
Because women have different biology and risk factors, researchers need to do a better job at including women in cardiology clinical trials – a point that is illustrated by the JAMA study.
For example, women with pregnancy complications such as eclampsia, high blood pressure and gestational diabetes have a higher risk of CVD.6 Though representation of women in cardiology clinical trials is improving, women are still underrepresented. According to a 2020 report, women made up only 38.2% of participants in cardiovascular clinical trials between 2010 and 2017.7
Nor should women be considered a homogeneous group. Just as data about men can’t be extrapolated to women, data on white women can’t be extrapolated to women of other racial or ethnic groups, who may have different CVD risk factors, incidences and survival rates.2 A weakness of the JAMA study acknowledged by its authors is that the majority of participants (86.5%) were white women. Efforts must be made to increase the diversity of subjects, including by identifying barriers to participation, such as language, and meeting subjects where they are, i.e., in the community rather than a medical center.
Lastly, the study emphasizes the need to treat women in a comprehensive and multidisciplinary manner. Patients’ conditions usually don’t fall into distinct silos labeled “cardiology” or “breast cancer,” for instance. Six in 10 Americans have at least one chronic disease and 4 in 10 have two or more chronic diseases, according to the CDC.8 And new research, including this study, is increasingly demonstrating that age-related degenerative diseases such as heart disease and cancer are interrelated, meaning that developing one may increase a patient’s odds of developing another.
The flip side of this interrelatedness is that adopting healthy habits that reduce the risk of one chronic age-related degenerative disease, such as CVD, also can potentially reduce the risk of others. An estimated 80% of CVD, for example, is preventable by altering modifiable risk factors and “knowing your numbers,” according to the World Health Organization.9 This means – if CVD is a risk factor for advanced breast cancer – that a large percentage of breast cancer is preventable too.
This study underscores the need for further research into the link between cardiovascular disease and breast cancer. Equally important is raising awareness about routine breast cancer screenings and preventive measures, while fostering a multidisciplinary approach that ensures comprehensive care.10 True progress lies not just in research but in breaking down silos—so every woman receives the holistic, proactive treatment she deserves.
