Breast Cancer Radiation May Increase Risk of Heart Disease

A study by British researchers and colleagues has found that radiation for breast cancer slightly increases a woman’s risk for heart problems. Women and their doctors should be aware of the risk when discussing breast cancer treatment, they say. Awareness can also help women who have had breast radiation make informed choices about lifestyle behaviors that can affect their risk of heart disease.

Radiation is often given after breast-conserving surgery to help lower the chance that the cancer will come back in the breast or nearby lymph nodes. Radiation may also be recommended after mastectomy in patients with a large tumor, or when cancer is found in the lymph nodes.

Because the heart is near the breasts—especially the left one—it is often exposed to some of the radiation. The study, published in the March 14, 2013 issue of the New England Journal of Medicine, estimated how much this exposure was likely to increase a woman’s risk of heart disease.

Calculating increased risk

Researchers studied the medical records of 2168 women in Sweden and Denmark who had radiation for breast cancer between 1958 and 2001. They estimated that the heart was exposed to, on average, a total of 4.9 units of radiation—called grays—during radiation of the breast.

The rate of major heart events was found to increase slightly with each gray. Major heart events included heart attack, the need to unblock or replace blood vessels to the heart, or death from a reduced blood supply to the heart (ischemic heart disease). For women who already had risk factors for heart disease, the risk of a major heart event increased a little more. But overall the increased risk was still very small.

For example, for a 50-year-old woman with no pre-existing heart risk factors, a 3-gray dose of radiation would increase her risk of having a major heart event before age 80 by 0.9% (from 4.5% to 5.4%). If she had one or more pre-existing heart risk factors, a 3-gray dose of radiation would increase her risk of having a major heart event before age 80 by 1.7%.

Talk to your doctor

The study’s authors point out that while doses of radiation to the heart are now lower than they were during the study’s treatment period, in most women the heart still receives a total dose of 1 to 5 grays.

Radiation is often an important part of treatment for breast cancer, helping to lower the chances that the cancer will return. Still, women considering breast cancer treatment and their doctors need to take the risks of treatment—including the slightly increased risk of heart disease—into account when making treatment decisions. This is especially important in women who have known risk factors for heart disease.

Women who have already had radiation treatment for breast cancer should make sure their primary care doctor knows about it, so they can receive appropriate follow-up care. Heart disease is the most common cause of death among all women. In women who have had breast radiation, taking steps to lower your risk of heart disease—such as not smoking, staying at a healthy weight, exercising, and eating a healthy diet, as well as getting cholesterol and blood pressure checks—is even more important.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master's-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Risk of Ischemic Heart Disease in Women after Radiotherapy for Breast Cancer. Published in the March 14, 2013 issue of the New England Journal of Medicine (Vol. 368, No. 11). First author: Sarah C. Darby, PhD, University of Oxford, Oxford UK.

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