Breast cancer radiation boosts heart disease risk

Women who received radiotherapy treatment for breast cancer in the 1970s and 1980s have an increased risk of dying from cardiovascular disease, and this risk is even greater if the left breast was treated, according to a study published in BMC Cancer.

British researchers analyzed data on 20,871 women from the Thames Cancer Registry in England and found that women with left-sided breast cancer who received radiotherapy from 1971 to 1988 had a 27% increased risk of dying from cardiovascular disease over women with right-sided disease who did not receive this treatment. The chance that these women would die from heart attacks and related conditions also was 25% higher than women who received radiotherapy only on the right side. The study appeared in the Jan. 15 issue.

Radiotherapy during this era frequently hit the heart. This study is the latest to document that, although the treatment strategy markedly decreased breast cancer mortality, its benefit is somewhat offset by a long-term increase in heart trouble.

"It's a very important issue in patients who receive left-sided breast radiotherapy," said Catherine Park, MD, assistant professor of radiation oncology at the University of California, San Francisco. She was not involved with this study. "We're very concerned about the heart."

But while the problem is increasingly recognized, it's still unknown what, if anything, should be done regarding heart care for these women.

"This is the most important question that we don't really know the answer to," said Eleanor Harris, MD, associate professor of radiation oncology at the H. Lee Moffit Cancer Center and Research Institute in Tampa, Fla., who was not affiliated with this study. "We don't know if we should be doing more screening or more intervention in these women."

Dr. Harris hopes to study the characteristics of radiotherapy-associated heart damage to determine interventions to address them. Until more is known, experts suggest that primary care physicians know about the existence of this heart disease risk factor.

"It's important that [they] be aware that their patients who have had radiation have an increased risk of cardiovascular disease because they are not followed by their oncologists any more," said Sharon Giordano, MD, MPH, a medical oncologist and assistant professor at the University of Texas MD Anderson Cancer Center.

Consideration also should be given to being more aggressive about modifiable risk factors. For example, a study in the September 2006 Journal of Clinical Oncology by Dr. Harris found that the increased cardiac risk in patients who received radiotherapy on the left side was even higher if they also had hypertension.

"These factors should be normalized if they're found to be abnormal," Dr. Harris said.

But concerns about the long-term impact apply not just to the women who received radiotherapy a few decades ago. Researchers also are assessing the impact of more modern radiotherapy and whether these women also should be considered at higher risk of heart disease.

Several studies have suggested that technical and methodological improvements since the mid-1980s that reduce the heart's exposure to radiation have achieved a better balance between curing the cancer without adding to a woman's risks for future illness and death. Experts caution, however, that since this adverse event does not show up until 10, 15 or more years after treatment, it may still be too early to know this for sure.

"There the jury is still divided. Hopefully, more data will come out," said Abram Recht, MD, who wrote an editorial on the subject accompanying Dr. Harris's 2006 paper. He is a professor of radiation oncology at Harvard Medical School in Boston. "We want to kill the cancer. We would prefer not to kill the patient."

Meanwhile, those who treat cancer point out that the risks documented thus far are not reasons for patients to avoid radiotherapy, and that these findings mark in part the success of treatment, since many more women are surviving breast cancer to reach the age where heart disease becomes the more important issue.

"Women are living a very long time after breast cancer, but all treatments have potential side affects," Dr. Harris said. "We just need to be aware of what the side effects are."