External Beam Radiation Impairs Endothelium-Dependent Vasodilation
External beam radiation significantly impairs endothelium-dependent vasodilation in the areas of the body that received radiation treatment, according to a report in the March 1st issue of the Journal of the American College of Cardiology.
This finding, the researches say, may help explain the increased risk of adverse vascular events among patients who receive external beam radiation. Dr. Joshua A. Beckman, from Brigham and Women's Hospital, Boston, and colleagues, studied breast and axilla arteries in 16 women who had been exposed to external beam radiation during treatment for unilateral breast cancer. Radiation treatment of these women occurred more than 3 years before the beginning of this study, according to the report.
In addition, the researchers analyzed arteries in 10 healthy women. "We found that endothelium-dependent vasodilation, which is a marker of the bioavailably of nitric oxide, was chronically decreased in patients who had external beam radiation. The effect was only seen in the areas that received the radiation and not in the rest of the body," Dr. Beckman told Reuters Health.
No impaired endothelium function was found in the vessels of control subjects. Decreased bioavailability of nitric oxide may be one mechanism which predisposes vessels that have been irradiated to increased rates of stenosis, Dr. Beckman explained. "It may partly explain why patients who receive chest or head and neck radiation are at an increased risk for myocardial infarction and stroke," he added.
Dr. Beckman was quick to point out that the effects of external radiation are different from the small doses of radiation delivered to individual vessels during intravascular brachytherapy. "Many studies have shown that intravascular brachytherapy is beneficial in preventing restenosis, and this study has no impact on those results," he said. Given these findings, Dr. Beckman said that researchers need to look at possible interventions and therapies to see if anything can be done to prevent or ameliorate the effect of external beam radiation and reduce the risk of vascular complications.
For now, Dr. Beckman recommends that patients who undergo external beam radiation therapy pay attention to how they feel. "If there are symptoms related to arterial insufficiency, such as chest pain or a temporary ischemic accident, then they should alert their physician right away," he told Reuters Health.
J Am Coll Cardiol 2001;37:761-765.
Thanks to Reuters Health
Science July 13, 2001
John Gofman, MD, PhD and
Egan O Connor, Editor
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