TUESDAY, March 6, 2007 (HealthDay News) -- Women who received radiation treatment for breast cancer during the 1980s appear to be at a higher risk of getting heart disease than women in the general population, a new study suggests.
Even so, the researchers emphasized that the benefit the women received from the radiation far outweighs any heart risk. That's because radiation treatment has been proven in other studies to improve the chances of breast cancer survival.
The study is published in the March 7 issue of the Journal of the National Cancer Institute.
Experts have long known that radiation therapy given to breast cancer patients in the 1960s and 1970s boosted the risk of death from heart disease. However, the picture has been less clear for women who underwent radiation regimens during the 1980s.
"Some reported increased risk of heart disease; others not," said Dr. Maartje Hooning, a researcher at the Netherlands Cancer Institute in Amsterdam and the study's lead author.
Hooning's team looked for differences in the incidence of heart disease among more than 4,400 breast cancer patients who had survived 10 years and were originally radiated between 1970 and 1986. They chose 10-year survivors, because it is believed the risk of heart disease does not emerge until a decade after treatment.
About half of the women were treated during the period 1970 to 1980; the other half between 1981 and 1986. Patients had either surgery and radiation; surgery, radiation and chemotherapy; or surgery alone.
After a median follow-up of 18 years, Hooning's team found 942 cases of cardiovascular disease in the group, most commonly heart failure. Participants also had an increased risk of heart attack and chest pains (angina) due to a lack of oxygen in the heart, compared to the general population.
Those who had radiation therapy were more likely to have heart disease risk than patients who had surgery alone, the study authors found. When they looked at the surgery-only group, those women had a lower risk of heart attack than the general population.
Patients treated with radiation earlier, before 1980, had about 1.5 times the heart disease risk of those who did not get radiation. Those treated with radiation after 1980 had a 1.35 times greater risk than those who didn't get radiation -- an increase that was not statistically significant.
The body region irradiated made a difference, too, with those who got radiation nearer the heart more likely to suffer heart problems.
"We found not only for patients irradiated during the 1970s, but also during the period 1980-86, moderately increased risk of heart failure and valvular dysfunction for certain radiation fields," said Hooning. "For patients treated after 1980, the risk of heart attack was not increased any more. We found that the effect of radiotherapy on cardiovascular disease was stronger among smokers."
Smokers who got radiation therapy had three times the risk of heart attack compared to nonsmokers who did not get radiation therapy.
How does radiation boost heart risks? It's not completely known, Hooning said. "There is a lot of research going on to unravel the mechanism involved in radiation-induced heart disease. According to the latest insights, radiation may damage the lining of small vessels in the heart muscle leading to a low oxygen level locally, and, after many years, to slowly progressive fibrosis of the heart muscle."
For patients undergoing radiation today, she said, the risk is presumed to be lower due to improved techniques.
Another expert, Dr. Sharon Giordano, assistant professor of medicine at the University of Texas M.D. Anderson Cancer Center, Houston, has also studied the impact of radiation therapy on cardiac risk of breast cancer survivors. She co-wrote an editorial to accompany the study.
"From our study and this study, too, the rates of cardiovascular disease are lower in the 1980s than patients treated back in the '70s," she said. "I think there is pretty clear evidence that the risk of cardiovascular disease due to radiation diminishes over time, but it's not clear whether the risk is eliminated."
Even so, Giordano said, the benefits of the radiation therapy, when it is indicated, are thought to outweigh the risks.
There are some ways women who are breast cancer survivors can modify their risk. "We should advise them to control and treat any existing cardiovascular risk factors, like high blood pressure, diabetes mellitus, high cholesterol, and, of course, to stop smoking," Hooning said.
Giordano agreed. "Smoking is a very bad idea for anybody but particularly if you are going through radiation therapy," she said.
"It's also important to get screened for early detection," she said. "If you are diagnosed in early stages, you may not need radiation, or may need less of it."
There's more on radiation therapy at the American Cancer Society.