October 28th, 2013

Radiation Dose Linked to Cardiac Risk in Breast Cancer Patients

In the past, cardiovascular risk has been linked to the radiation dose received by breast cancer patients. Now, a new study published in JAMA Internal Medicine attempts to calculate the cardiac risk of breast cancer patients today undergoing current radiotherapy protocols.

David J. Brenner and colleagues calculated the excess cardiac risk for 48 patients who received radiotherapy at New York University. They estimated the 20-year cardiac risk based on baseline risk and patient-specific mean cardiac radiation dose. Cardiac dose was significantly higher in patients with left-sided radiotherapy. These patients also received significantly higher doses if they were treated in the supine body position instead of the prone position. Position did not significantly have an impact on cardiac dose in patients who received right-side radiotherapy.

Patients with the highest baseline risk who had left-sided therapy treated in the supine position therefore had the highest amount of estimated radiotherapy-induced risk (3.52%, CI 1.47%-5.85%). By contrast, low-risk patients with right-sided radiotherapy had only a small increased risk (<0.1%).

The authors conclude that in patients at high baseline risk “radiotherapy-induced risks of major coronary events are likely to be reduced… by targeting baseline cardiac risk factors (cholesterol, smoking, hypertension), by lifestyle modification, and/or by pharmacological treatment.”

In an invited commentary, Carolyn Taylor and Sarah Darby write that the large variability in the cardiac risk associated with radiotherapy can provide “reassurance for the majority of women that their absolute risk of ischemic heart disease from breast cancer radiotherapy is likely to be small compared with the likely absolute benefit…” For some patients, however, a risk estimate may identify “the minority of women for whom the benefits of radiotherapy do not clearly outweigh the risks, including those for whom adequate coverage of the target tissue cannot be achieved without a high heart dose.”



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