Among patients with early stages of breast cancer, those whose hearts were more directly irradiated with radiation treatments on the left side in a facing-up position had higher risk of heart disease, according to new research.
Several reports have suggested links between breast cancer radiation and long-term cardiovascular-related deaths, according to background information in the research, which was published Oct. 28 on the website of JAMA Internal Medicine.
David J. Brenner, PhD, DSc, of Columbia University Medical Center in New York City, and colleagues examined the radiation treatment plans of 48 patients with stage 0 through II-A breast cancer who were treated after 2005 at the New York University Department of Radiation Oncology. They calculated the association between radiation treatment factors, such as average cardiac dose, cardiac risk, treatment side, body positioning and coronary events.
According to the study results, the greatest increased risks were seen for left-sided treatment in women of high baseline risk who were treated in the supine position. The treatment-induced additional risk in these cases was 3.52%. The lowest risks, increasing less than 0.1%, were for right-sided treatment in low-baseline risk women.
In left-sided radiation, prone position reduced cardiac doses and risks, while body positioning had little effect in right-sided therapy (where the heart is always out of field), the researchers reported.
Because the effects of radiation exposure on cardiac disease seem to be multiplicative, the highest absolute radiation risks correspond to the highest baseline cardiac risk, the authors concluded. Consequently, radiotherapy-induced risks of major coronary events are likely to be reduced in these patients by targeting baseline cardiac risk factors (cholesterol, smoking, hypertension), by lifestyle modification and/or by pharmacological treatment.
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