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 or history of prior breast radiation therapy Breast cancer requiring bilateral breast/chest wall radiation therapy Undergoing concurrent chemotherapy treatment Documented fall risk Active known or suspected systemic autoimmune disease (except for vitiligo, residual auto-immune hypothyroidism requiring hormone replacement only, psoriasis not requiring systemic treatment for two years, conditions not expected to recur in the absence of an external trigger) or any history of a systemic inflammatory arthritis such as psoriatic, rheumatoid, systemic lupus, ankylosing spondylitis or reactive arthritis Uncontrolled intercurrent illness including, but not limited to: 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-angiotensin system (RAS) agent Agents to increase serum potassium Lithium Aliskiren for diabetes Having a known allergy to any active or inactive ingredient in Losartan Unable to tolerate oral medication Pregnant or breast-feeding or planning pregnancy for the year following radiation The presence of interstitial lung disease on baseline CT scan Patients with any medical condition, including findings in laboratory or medical history or in the baseline assessments, that (in the opinion of the Principal Clinical Investigator or his/her designee), constitutes a risk or contraindication for participation in the study or that could interfere with the study conduct, endpoint evaluation or prevent the subject from fully participating in all aspects of the study Individuals known to possess deoxyribonucleic acid (DNA) gene mutations including: Ataxia-Telangiectasia Mutated (ATM) Double-strand-break repair protein rad21 homolog (RAD21) C-to-T single-nucleotide polymorphism (C-509T) in the Transforming growth factor β-1 gene