Patients with breast cancer receive low doses to smaller volumes of the heart, but they also have an excellent long-term survival, so it is crucial to study the effects of low dose radiotherapy. Indeed, a recent study suggests that these effects can be seen within the first 5 years after treatment, and that there is no dose threshold. The investigators wish to develop imaging and blood biomarkers of cardiac exposure, as a first step to identifying patients at increased risk for cardiac effects. These patients can then be targeted for close monitoring and early intervention, potentially with statins or ACE inhibitors. Additionally, by characterizing a time-course and radiation dose-volume relationship, potentially real-time modifications can be made to radiotherapy (RT) field design for patients sensitive to RT effects. Finally, this information can be incorporated into better designs of treatment plans for future patients.

Radiotherapy plays an integral role in breast cancer therapy. Multiple randomized studies have demonstrated decreased local-regional recurrence rates and decreased breast-cancer mortality. However, balanced with this survival benefit is the potential toxicity of the treatment itself. In particular, cardiac effects of radiotherapy have been a concern and an area of research for the past 20 years. From long-term follow up of patients with lymphoma, it is known that radiotherapy can lead to increased risk of myocardial infarction, valvular dysfunction, systolic and diastolic function abnormalities, and heart failure among cancer-survivors. Patients with breast cancer receive lower doses to smaller volumes of the heart, but they also have an excellent long-term survival, so it is crucial to study the effects of low dose radiotherapy. Indeed, a recent study suggests that these effects can be seen within the first 5 years after treatment, and that there is no dose threshold. The investigators hypothesize that they can develop imaging and blood biomarkers of cardiac exposure, as a first step to identifying patients at increased risk for cardiac effects. These patients can then be targeted for close monitoring and early intervention, potentially with statins or ACE inhibitors. Additionally, by characterizing a time-course and radiation dose-volume relationship, potentially real-time modifications can be made to RT field design for patients sensitive to RT effects. Finally, this information can be incorporated into better designs of treatment plans for future patients.

Inclusion Criteria:

• Patients who will receive radiotherapy as treatment for left-sided breast cancer
• Patients must understand and be willing to sign an informed consent form approved for this purpose by the Institutional Review Board (IRB) of the University of Michigan Medical Center indicating that they are aware of the investigational aspects of the treatment and the potential risks.

Exclusion Criteria:

• Patients with a contraindication to contrast-enhanced MRI

Patients receiving radiotherapy for treatment of left-sided breast cancer.