Standard of care for locally advanced breast cancer (LABC) requires neoadjuvant treatment to downstage tumors before surgery. However, many low/middle income country patients cannot afford this treatment due its high cost. At the Cancer Institute (INCAN) Guatemala, most patients never begin or complete treatment. For hormone receptor positive (HR+) breast cancer, neoadjuvant endocrine therapy with tamoxifen (TMX) has proven effective at a much lower cost. This study evaluates the feasibility, adherence, and efficacy of neoadjuvant TMX in a low-resource setting in Guatemala.