Breast Cancer Radiation Therapy and the Heart

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Question: Breast Cancer Radiation Therapy and the Heart

I had a lumpectomy and radiation therapy five years ago for early-stage breast cancer. My cancer is gone, and my doctor says I have an excellent prognosis — at least as far as the cancer is concerned. However, he says I need to be careful about heart disease, since the chest radiation I was exposed to may increase my risk for a heart attack. How high is my risk for heart disease?

And when doctors say, "Be careful about heart disease," what are they talking about?

Answer: Many women who have breast cancer receive radiation therapy (RT) as a part of their treatment regimen. There is a very good reason for this. For over 30 years, studies have shown that RT after a lumpectomy or mastectomy significantly improves survival from breast cancer.

Unfortunately, early studies in women receiving RT also showed that the subsequent risk of developing a variety of heart problems was increased. For this reason, since about 1980 the techniques used to deliver RT have been modified specifically to minimize the amount of radiation the heart receives. As a result, the excess risk of heart disease following RT for breast cancer has been greatly reduced.

What Types of Heart Problems Are Associated With Breast Cancer RT?

In the early years of breast cancer RT, before the cardiac risk had been identified, the radiation dose received by the heart was substantially larger than it is today.
Before too long, some doctors began noticing several varieties of heart disease in women following RT. The most common heart problem experienced by these women was premature coronary artery disease (CAD). That is, CAD began appearing in women in their 40's or 50's, or even in their 30's following RT.
Other kinds of cardiac problems attributed to RT included cardiomyopathy, pericarditis, valvular heart disease, and cardiac arrhythmias (especially bradycardias). The recognition that RT to the chest area could induce heart disease led specialists to devise new ways to "shield" the heart from radiation exposure during RT.

As a result, cardiac risk has been substantially reduced with modern RT techniques. However, not all the risk has been eliminated; some degree of added cardiac risk remains after RT for breast cancer. Most of this remaining risk appears to be a risk of developing CAD. The post-radiation cardiomyopathy, pericarditis, heart valve disease and arrhythmias are now rarely reported.

How High Is the Risk?

For women who have received RT since about 1980, the excess risk of having a heart attack or dying from CAD is relatively small. As an example, one large study estimated that if a 50-year-old woman had RT for breast cancer, and she had no other major risk factors for CAD, her risk of dying from heart disease before age 80 would be increased by less than 1%.
So while there is still some increased risk, the magnitude of the increase is small.

Left Breast Cancer v. Right Breast Cancer

Because the heart is almost always located in the left side of the chest, it is not surprising that in early studies the risk of developing heart disease was significantly higher in women who were treated for cancer of the left breast than for cancer of the right breast. However, in recent years, owing to modern shielding techniques that reduce cardiac radiation even with cancer of the left breast, the "extra" risk seen in women with left-sided breast cancer has been substantially reduced. Indeed, it has become difficult to measure a higher level of risk in women with cancer of the left breast.

What Can You Do To Reduce Cardiac Risk?

The most practical way to look at the cardiac risk posed by breast cancer RT is to view it simply as one of several risk factors you may have for developing CAD. And, as is always the case, the more risk factors you have, the higher your overall risk for CAD.

This means that, if you have had RT, it is even more important for you to minimize all the risk factors over which you do have substantial control. You should eat a heart-healthy diet, monitor your weight, get plenty of exercise, avoid tobacco, and make sure your cholesterol levels and blood pressure are in a healthy range. If you do these things your overall risk for developing heart disease - despite the RT you have received - is likely to remain quite low.


RT is an important part of therapy for many women with breast cancer. While RT applied to the chest does increase the subsequent risk of heart disease, that excess cardiac risk with the technology being used today is small, especially when compared to the reduced risk of dying from breast cancer.

Furthermore, even if you've had RT for breast cancer, your overall risk of developing CAD is something that is largely within your control. By making the right lifestyle choices and by working with your doctor to control your cardiac risk factors, you can greatly minimize your risk of heart disease.


Clarke M, Collins R, Darby S, et al. Effects of radiotherapy and of differences in the extent of surgery for early breast cancer on local recurrence and 15-year survival: an overview of the randomised trials. Lancet 2005; 366:2087.

Darby SC, Ewertz M, McGale P, et al. Risk of ischemic heart disease in women after radiotherapy for breast cancer. N Engl J Med 2013; 368:987.

Moslehi J. The cardiovascular perils of cancer survivorship. N Engl J Med 2013; 368:1055.

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