A new risk calculator may help identify women who are most likely to develop heart failure years after treatment for early-stage breast cancer, and it shows that older age and traditional cardiovascular risk factors are key drivers.

In a study of over 26,000 women treated for local or regional breast cancer, the risk prediction model was able to prospectively identify those at a high risk of developing heart failure and/or cardiomyopathy over 10 years.

With further validation, the risk calculator could offer a “practical tool” for spotting patients most at risk for heart conditions and considering preventive strategies, lead researcher Ana Barac, MD, PhD, chair of cardio-oncology at Inova Schar Heart and Vascular in Fairfax, Virginia, told Medscape Medical News.

The findings were published on October 23 in JAMA Oncology.

Previous research has shown that breast cancer survivors have a higher risk for cardiovascular death than the general population, partly due to cardiotoxicity from certain treatments, including anthracyclines and trastuzumab. Guidelines recommend cardiac assessments for patients receiving either of those therapies.

However, there are no validated tools for estimating cardiovascular risk in patients receiving other breast cancer therapies or those who have traditional risk factors for cardiovascular disease. In addition, routine cardiac monitoring of all patients receiving trastuzumab has raised concerns about overimaging, Barac’s team pointed out, underscoring a need for more personalized risk-based approaches.

The new study, Barac said, was designed to create and test a risk prediction model that incorporates not only a patient’s cancer and cancer treatment characteristics but also their preexisting cardiovascular risk factors, including older age, hypertension, diabetes, smoking, and obesity.

The researchers used data from 26,044 patients aged 18-79 who were diagnosed with stage I-III breast cancer at Kaiser Permanente Southern California between 2008 and 2020. The group was randomly split into derivation (60%) and validation (40%) cohorts.

First, the researchers identified individual risk variables. Not surprisingly, age stood out: Women aged 65-74 had 3.5 times the risk of developing heart failure/cardiomyopathy vs women younger than 40 (hazard ratio [HR], 3.49; P < .001). The risk was also elevated among patients with hypertension (HR, 2.02; P < .001) and among those treated with anthracyclines (HR, 1.95; P < .001) or HER2-targeted therapy without anthracycline chemotherapy (HR, 1.66; P < .001).

Other cardiovascular risk factors, including diabetes, smoking, and obesity, were also significant contributors to the risk of developing heart failure/cardiomyopathy. But neither radiotherapy nor endocrine therapy increased the risk, while non-anthracycline chemotherapy had a modest effect (HR, 1.21; P = .046).

For their risk calculator, the researchers created weighted scores for each of the significant risk variables. They then divided both cohorts into low-, medium-, and high-risk groups, with 10-year estimated risks for heart failure/cardiomyopathy of 1.3%, 6.3%, and 19.4%, respectively.

Overall, Barac’s team found that the calculator’s discrimination was good, with a time-dependent area under the curve of 0.79 for estimating 10-year risk in the validation cohort. That was within the acceptable range for clinical use, the researchers noted.

One message from the findings is that “cancer treatment alone is insufficient to lead to high-risk categorization,” according to an editorial published with the study. In fact, the “driving force” was older age and traditional cardiovascular risk factors, wrote Patricia Ganz, MD, and Eric Yang, MD.

The bottom line is that breast cancer survivors’ heart health needs to be on the radar, said Ganz, of the UCLA Jonsson Comprehensive Cancer Center.

Not all breast cancer survivors need to see a cardiologist, both Ganz and Barac stressed. But they all do need, at a minimum, access to primary care that addresses their cardiovascular risk factors.

“Basically, we need somebody who’s minding the cancer store and somebody who’s minding the general medical store,” Ganz told Medscape Medical News.

The “conversation” around cardiovascular health may begin in the oncologist’s office, Barac said, but primary care and cardiology should be involved as appropriate.

As for the risk calculator itself, Ganz noted in the editorial that it may underestimate the risk for heart failure after breast cancer: The study population was insured and lived in an area of the US with a relatively low rate of heart failure, making validation in other populations and settings essential.

Ganz pointed out that breast cancer survivors’ cardiovascular health is a critical issue that will only continue to grow in scope. In the US alone, there are 4.3 million women with a history of breast cancer, with projections of another million by 2035.

The study was funded by the National Institutes of Health and Georgetown Lombardi Comprehensive Cancer Center. A co-author reported receiving personal fees from UpToDate and Pfizer. Ganz reported receiving grants from the Breast Cancer Research Foundation and personal fees from UpToDate, Astellas, and Informed DNA.

Keith Mulvihill is a freelance journalist based in New York City.