Radiation treatment for breast cancer can increase a woman's risk of heart disease, doctors have long known. But the size of the added risk has not been clear.
Now, a new study offers a way to estimate the risk. It finds that for most women the risk is modest, and outweighed by the benefit from the treatment, which can halve the recurrence rate and lower the death rate from breast cancer by about one-sixth.
According to the study, a 50-year-old woman with no cardiovascular risk factors has a 1.9 percent chance of dying of heart disease before she turns 80. Radiation treatment for breast cancer increase that risk by 2.4 percent to 3.4 percent, depending on how much radiation hits the heart.
"It would be a real tragedy if this put women off having radiotherapy for breast cancer," said Sarah Darby, a professor of medical statistics at the University of Oxford in Britain, and the lead author of the study, published Wednesday in The New England Journal of Medicine.