Radiation for breast cancer can increase heart risks

When my mother was treated for breast cancer several years ago, she had just one objective in mind: to eradicate the cancer. For her, radiation therapy was the best way to do that.

Radiation, on its own or coupled with other treatments, has given many women like my mother the chance to survive their breast cancer. Yet years later, some of these women are encountering a residual side effect from their radiation—heart disease.

A new research letter published in JAMA Internal Medicine estimates that the increased lifetime risk for a heart attack or other major heart event in women who’ve had breast cancer radiation is between 0.5% and 3.5%. The risk is highest among women who get radiation to the left breast—understandable, since that’s where the heart is located.

The heart effects of radiation begin emerging as soon as five years after treatment, according to a large European study out earlier this year in The New England Journal of Medicine. That study also found that, for every 1 gray of radiation (a unit that measures the absorbed radiation dose), a woman’s heart risk rises by 7.4%. “Even small doses of radiation can cause trouble,” says Dr. Alphonse Taghian, professor of radiation oncology at Harvard Medical School and chief of breast radiation oncology at Massachusetts General Hospital.

Treat breast cancer, protect the heart

Future heart risks should not be the reason to abandon this important component of treatment. “I don’t think by any means it should make anyone forego radiation for breast cancer therapy,” says Dr. Javid Moslehi, instructor in the department of medicine at Harvard Medical School, and co-director of the cardio-oncology program at Brigham and Women’s Hospital.

“The ultimate goal is to minimize the exposure to the heart as much as possible,” Dr. Taghian says.

In the JAMA study, researchers found that having a woman lie on her stomach during radiation treatment reduced her exposure. Dr. Taghian uses a technique called the breath-hold with his patients. Holding a breath expands the lungs, which pushes the heart out of the radiation’s path. This technique can cut radiation exposure to different structures of the heart by 54% to 96%.

Protecting women from the side effects of radiation is not a one-size-fits-all approach. “I don’t think there is one method to fit all patients,” he says. “The bottom line is we have to try the optimal method for each patient to avoid exposing the heart.”

Proton therapy—a relatively new radiation treatment that uses particles instead of traditional x-rays—can also lower a woman’s exposure, but very few centers currently offer this treatment. “In the future, this will probably be the dominant way to spare the heart,” Dr. Taghian says.

Know your heart risks

Before having radiation for breast cancer, a woman should have a discussion with her oncologist—as well as her cardiologist. Ask the oncologist what dose of radiation you’ll be getting, and how your heart will be protected during treatment. Talk to your cardiologist about your existing heart risks, and how to reduce them.

It’s especially important to consider your heart if you’re also having chemotherapy, which is well known for its cardiotoxicity. “We can’t avoid the heart risks with chemotherapy, but with radiation we could lower them using better technology and better understanding,” Dr. Taghian says.

Though you may not be able to fully protect your heart from cancer treatment, there are other lifestyle-based heart disease risks you can control. In the JAMA research letter, women who were least likely to develop heart disease were those who were already at low risk based on their cholesterol, blood pressure, and C-reactive protein (a marker of inflammation) levels. “Make sure the blood pressure is under control, you’re not smoking, you have a healthy lifestyle, and you control your cholesterol,” Dr. Moslehi advises.