Radiation, on its own or coupled with other treatments, has helped many women survive breast cancer. Yet radiation therapy can cause the appearance of heart disease years later. New research 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. However, future heart risk should not be the reason to abandon this important component of treatment. Cancer experts are doing more and more to minimize the amount of radiation the heart receives.