Women undergoing radiotherapy for breast cancer face a modestly higher risk of heart disease, according to a European study.
“Radiotherapy for breast cancer often involves some incidental exposure of the heart to ionizing radiation,” researchers wrote in the March 14 issue of the New England Journal of Medicine, but the effect regarding subsequent risk of ischemic heart disease is uncertain.
Researchers with the Clinical Trial Service Unit at the University of Oxford in England conducted a population-based case-control study of major coronary events (myocardial infarction, coronary revascularization or death from ischemic heart disease) in 2,168 women who underwent radiotherapy for breast cancer between 1958 and 2001 in Sweden and Denmark. Among the cohort, 963 women experienced major coronary events.
Individual patient information was obtained from hospital records. For each woman, researchers estimated average radiation doses to the whole heart and to the left anterior descending coronary artery using data from the patients radiotherapy chart.
The overall average dose to the whole heart was 4.9 grays. Rates of major coronary events increased linearly with the average dose to the heart by 7.4% per gray. The increased risk started within the first five years after radiotherapy and continued into the third decade after.
The researchers determined that a 50-year-old woman with no cardiovascular risk factors has a 1.9% chance of dying of heart disease before age 80. Radiotherapy for breast cancer would increase that risk to between 2.4% and 3.4%, depending on how the level of radiation to which the heart was exposed.
Still, it “would be a real tragedy if [the findings]put women off having radiotherapy for breast cancer,” Sarah Darby, PhD, the studys lead author, told the New York Times.
The study abstract is available at www.nejm.org/doi/full/10.1056/NEJMoa1209825?query=featured_home.