The global burden of cancer continues to rise with an incidence of 17.5 million cancer cases worldwide. Approximately 50% of all cancer patients receive radiation therapy as a component of their cancer care. While radiation therapy has demonstrable benefit in improving survival in patients with many types of malignancies, cardiotoxicity is a major concern in patients receiving chest radiotherapy. The rates of major coronary events increased by 7.4% per gray of mean heart dose; the increased risk was noted within the first 5 years of radiotherapy and persisted into the third decade after treatment. With improvements in multi-disciplinary care of cancer patients, the long-term survival in patients with thoracic malignancies continues to improve and radiation-induced heart disease (RIHD) is now a major source of morbidity and mortality in such patients.In this study, the investigators will enroll five female patients (18 years of age to 100 years of age) with left-sided breast cancer who underwent lumpectomy or mastectomy without tissue expander placement and will receive adjuvant standard-of-care breast or chest wall radiation therapy. They will undergo baseline magnetic resonance spectroscopic imaging with \[1-13C\]pyruvate injection and a proton MRI/spectroscopy scan prior to receipt of adjuvant radiation therapy. Post-treatment imaging will be performed within 3 months of completion of radiation treatments. This study will investigate whether non-invasive MRI scanning approaches will detect damage to the heart from left-sided radiation treatments before structural changes and mechanical functional deficits become apparent. A first-in-human clinical study to evaluate the effect of cardiotoxic chemotherapy on \[1-13C\]Pyruvate metabolism is currently ongoing at UT Southwestern (ClinicalTrials.gov Identifier: NCT03685175; PI: Dr. Vlad Zaha). The proposed study employs the same technology and approach to study radiation-induced cardiac toxicity. The study will also test the prognostic value of decreased myocardial mitochondrial pyruvate flux in predicting clinically significant radiation induced cardiotoxicity. Towards this goal, study will measure myocardial mechanical functional parameters, including left ventricular global longitudinal strain and left ventricular myocardial deformation using cardiac MRI and correlate these changes with \[1-13C\]lactate/ \[13C\]bicarbonate ratio. Previous studies have demonstrated that strain rate imaging by MRI is a sensitive technique for dose-dependent decrease in myocardial function after breast radiotherapy. Although this pilot study is restricted to breast cancer patients, successful demonstration of feasibility will allow extension of the study to all patients receiving thoracic radiation (such as patients receiving radiation therapy for lung cancer, esophageal cancer and thoracic lymphomas). The lack of reliable technologies for early detection of sub-clinical radiation-induced cardiotoxicity limits early intervention in such patients. Thus, identification of early cardiac changes induced by radiation therapy at a stage that offers potential for reversibility remains a major unmet need in cancer care.

Concerns for sexually active men and women: Women should not become pregnant and men should not father a baby while taking part in this study because we do not know how the study drugs/procedures could affect a man's sperm (for some drugs/procedures, the concern may be that the sperm might be affected and in some cases, drugs could being carried by the semen into the vagina and cause harm) or a fetus, if a woman becomes pregnant during the study. It is important that you talk to your study doctor about avoiding pregnancy during this study. If you think you might have become pregnant or if you believe your female partner has become pregnant while you are in this study, you must tell one of the study doctors right away so that management of the pregnancy and the possibility of stopping the study can be discussed.