Losartan in Prevention of Radiation-Induced Heart Failure

This study is being done to see if losartan affects the chances of developing radiation-induced heart failure in patients who are receiving radiation therapy as part of standard of care treatment for breast cancer. The interventions involved in this study are: * Losartan * Radiation Therapy (standard of care)

This is a pilot study examining whether losartan prevents radiation therapy-induced myocardial fibrosis (thickening of the heart tissue), which can cause heart failure, in breast cancer patients receiving radiation therapy. Losartan is an U.S. Food and Drug Administration (FDA) approved drug used to treat hypertension (high blood pressure) and heart failure. The U.S. Food and Drug Administration (FDA) has not approved losartan for use in the treatment of breast cancer. The FDA has approved radiation therapy as a treatment option for breast cancer. The research study procedures include: screening for eligibility and study treatment including evaluations and follow up visits. It is expected participants will be on the study for 1 year. It is expected that about 10 people will take part in this research study.