Losartan to Reduce Radiation Induced Fibrosis in Breast Cancer Patients

Inclusion Criteria * Diagnosed with clinical or pathologic stage 0-IV invasive breast cancer to include ductal carcinoma in situ (Tis), primary tumor cannot be assessed (TX) and all other primary tumor stage categories (T1-T4) * Has been treated with breast conserving surgery or mastectomy with reconstruction * Is a candidate for unilateral post-surgery radiation therapy per National Comprehensive Cancer Network (NCCN) guidelines * Age ≥ 18 * Female * Laboratory values * Aspartate Aminotransferase (AST) ≤ 2.5 x Upper Limit Normal (ULN) * Alanine Aminotransferase (ALT) ≤ 2.5 x ULN * Creatine ≤ 1.5 x ULN * Estimated Glomerular Filtration Rate (eGFR) ≥ 60 Inclusion of Women and Minorities - Women of any race/ethnicity are eligible for this trial. Exclusion Criteria * Recurrent breast cancer and history of prior breast radiation therapy * Breast cancer requiring bilateral breast/chest wall radiation therapy * Undergoing concurrent chemotherapy treatment * Documented fall risk * Active known diagnosis of a connective tissue disorder, rheumatoid arthritis, or systemic lupus erythematosus (SLE) * Any known uncontrolled intercurrent illness including, but not limited to: * Hyperkalemia * Impaired renal function * Symptomatic congestive heart failure * Unstable angina pectoris * Kidney disease * Uncontrolled diabetes * Cystic fibrosis * Fibromyalgia based on American College of Rheumatology criteria * Concomitant use of: * Losartan * Other renin-angi…