Losartan to Reduce Radiation Induced Fibrosis in Breast Cancer Patients

This single site study will be conducted at the Vail Health Shaw Cancer Center in Edwards, Colorado. A block, double-blinded, placebo-controlled, randomized phase II design will be utilized . Study participants will be blocked by surgical intervention (breast conserving surgery vs. mastectomy) and then randomized, 1:1, into the treatment and control arms for a total of four study arms. The research team and study participants will be blinded to the study arm and a placebo will be used to reduce detection bias in the reporting of outcomes. Selection bias will be minimized through the randomization of study arms. Study participants will be prescribed 25mg capsules of placebo or the investigational drug, Losartan, to be taken by mouth once daily. The treatment start date will be the day that subject begins radiation therapy. Radiation therapy will continue to be prescribed in accordance with local clinic procedures. Treatment with the study intervention will continue for one year upon completion of radiation therapy. All participants will be assessed for fibrosis, cosmetic outcomes, and incidence of reoperation for 18 months following the completion of radiation therapy.