Cardiac MRI Detects Early Heart Stress After Breast Cancer Radiation
Dose and risk assessment can help inform personalized care, follow-up
A multicenter study using advanced imaging found modest, subclinical changes in heart structure and function in all patients at the two-year follow-up after radiation therapy for breast cancer, particularly those who had received higher cardiac doses.
The EARLY-HEART study followed 138 women across three institutions in Europe, and is part of the large, multi-country European Union research Implications of Medical Low Dose Radiation Exposure (MEDIRAD) project. MEDIRAD was conducted between Dec. 2017 and Sept. 2019 in response to concerns about radiation-induced heart disease in breast cancer survivors.
Using centralized cardiac MRI and validated automated strain measurement methods, researchers tracked detailed heart function metrics. They focused especially on left ventricular global longitudinal strain (LV GLS)—a sensitive early indicator of cardiac dysfunction that has been shown in other research to be predictive of long-term cardiac events, including heart failure, ischemic heart disease and heart attacks.
Cardiac MRI scans of the heart were performed at baseline, and six months and two years after lumpectomy and local radiation therapy. None of the patients received chemotherapy and all were asymptomatic for cardiovascular disease at baseline.
Two years after treatment, all participants had slightly smaller heart chambers and their hearts pumped out less blood. Specifically, there were decreases in left ventricular end-diastolic volume and stroke volume, along with an increase in cardiac remodeling.
All participants remained asymptomatic during the two-year follow-up. “It was difficult to analyze the results because the observations were small and detected only by sophisticated analysis,” said co-author Elie Mousseaux, MD, PhD, radiology professor, Paris Cité University, and at the Georges-Pompidou European Hospital in Paris. “The LV GLS stayed within the normal range for all except six patients, who had received the highest radiation doses.”
No cardiovascular deaths, hospitalizations or major clinical cardiac events—heart attacks, heart failure, arrhythmias, chest pain or shortness of breath—were reported during the study, however longer follow-up was not available.
“The relative risk increased by a factor between two and four in the subgroup of patients receiving the extra radiation compared to the others. This means the more radiation a patient receives during breast cancer radiation therapy, the greater the risk of subsequent decrease in longitudinal function.”
— ELIE MOUSSEAUX, MD, PHD
Subtle, Persistent Changes in Subgroup Receiving More Radiation
According to Dr. Mousseaux, technological advances in breast radiation have significantly reduced by more than half the cardiac doses commonly used 20 years ago. Yet this study, the largest of its kind, confirms earlier research findings that even the smallest radiation doses can cause functional changes in the heart.
Of note, 23 participants exhibited a persistent decrease in LV GLS, all of whom received higher mean radiation doses to the whole heart (2.09 Gy vs. 1.36 Gy) and left ventricle (2.40 Gy vs. 1.34 Gy) compared to those without GLS decline.
“The relative risk increased by a factor between two and four in the subgroup of patients receiving the extra radiation compared to the others,” Dr. Mousseaux said. “This means the more radiation a patient receives during breast cancer radiation therapy, the greater the risk of subsequent decrease in longitudinal function.”
This subgroup also exhibited a significant rise in the left atrial booster function, an indicator of the heart compensating for impaired filling, suggesting possible subclinical diastolic dysfunction.
All of these changes could represent early markers of heart failure with preserved ejection fraction (HFpEF), a condition that is often difficult to detect in its initial stages.
Personalizing Strategies for Heart Risk
Together, the observations underscore the need to shift from a one-size-fits-all approach to a more individualized follow-up strategy for patients at higher risk. “Now we can speak about personalized follow-up because we know exactly which patients received the highest cardiac radiation dose,” Dr. Mousseaux said.
He emphasized the importance of prioritizing other cardiovascular risk factors. “After 10 years, the risk of dying from heart disease for women treated by radiation therapy, chemotherapy or both, is up to six times higher than the risk for the general population of the same age and without any treatment. But in most cases, this is related to coronary artery disease and not heart dysfunction,” Dr. Mousseaux said. “Assessing risk factors for cardiovascular disease is very important—is she a smoker, does she have high cholesterol and so on. The radiation dose is one part of the risk.”
For More Information
Access the Radiology: Cardiothoracic Imaging study, “Cardiac MRI-based Subclinical Cardiac Dysfunction during 2 Years after Breast Cancer Irradiation: The MEDIRAD EARLY-HEART Study.”
Read previous RSNA News stories on cardiac imaging: