It has always been assumed that radiotherapy for breast cancer increases the risk of heart disease later in life. However, little has been known about the nature of the risk and if certain individuals are particularly susceptible to ionising radiation. The present study by researchers at Karolinska Institutet and their colleagues from Denmark and Britain has addressed these issues.

The study included almost 2,200 Danish and Swedish women who had received radiotherapy for breast cancer between 1958 and 2001. Information from radiotherapy charts and medical records were used to estimate mean radiation dose to the heart. The researchers gathered information about the medical history and risk factors for heart disease of each woman.

A clear correlation between radiation dose and risk of ischemic heart disease was revealed. The risk was particularly pronounced for women with diabetes, chronic obstructive lung disorders, angina or other heart diseases, a high BMI, or who were smokers at time of their treatment. The highest risks were noted during the first ten years following treatment, after which the risk decreased, but was still elevated 20 years after radiotherapy.

The risk of a subsequent ischemic heart disease was influenced by age at therapy, previous disorders and heart dose. Comparing a 50 year old breast cancer patient without previous risk factors for heart disease and who did not receive radiotherapy, to a woman of similar age with hypertension and high radiation doses to the heart (10 Gy), reveals approximately 3 times higher risk of ischemic heart disease in the treated patient.

“The results confirm what we have long suspected, that irradiation increases the risk of myocardial infarction, and that women with other known risk factors for ischemic heart disease are more susceptible than others,” says Per Hall, Professor of radiation epidemiology at Karolinska Institutet’s Department of Medical Epidemiology and Biostatistics. “This gives us stronger grounds on which to weigh the pros of irradiation against the cons of its harmful effects on the heart for individual patients.”

The study was made possible with funding under the EU’s Radiation Associated Cardiovascular Events (RACE) project. The research team also received grants from the UK Department of Health, the British Heart Foundation, and Cancer Research UK.

Publication: ‘Risk of Ischemic Heart Disease in Women Irradiated for Breast Cancer’, Sarah Darby, Marianne Ewertz, Paul McGale, Anna Bennet, Ulla Blom-Goldman, Dorthe Broennum, Candace Correa, David Cutter, Giovanna Gagliardi, Bruna Gigante, Maj-Britt Jensen, Andrew Nisbet, Richard Peto, Kazem Rahimi, Carolyn Taylor, Per Hall, New England Journal of Medicine, 14th March 2013.

Caption: Per Hall, credit Ulf Sirborn

For further information, please contact:
Per Hall, Professor of radiation epidemiology
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet
Tel: +46 (0)73-396 0590
Email: per.hall@ki.se