This is a one-arm phase II interventional study in patients with breast cancer to investigate whether memantine can prevent cognitive decline during chemotherapy. The investigators will recruit 56 participants referred to the University of North Carolina (UNC) Breast Center and affiliated outpatient clinics for initiation of adjuvant or neoadjuvant chemotherapy, perform a cognitive assessment within one week of initiating and four weeks after completion of chemotherapy, and treat with memantine 10 mg twice daily between the pre- and post-chemotherapy study assessments (estimated duration: 12-26 weeks, depending on the chemotherapy regimen). Cognitive function will be assessed objectively using a computerized cognitive assessment (Delayed Matching to Sample (DMS) test) and a standard neuropsychological battery. To assess subjective cognitive function, the Patient Reported Outcome Measurement Information System (PROMIS) Cognitive Function measure will be used. Depression, anxiety, fatigue, menopausal status, and sleep are comorbidities known to affect cognitive function, and therefore will be assessed as covariates pre- and post-chemotherapy. Depression, anxiety, health-related quality of life (HRQOL) and functional status will be evaluated as secondary outcomes. The feasibility of the investigator's study by monitoring recruitment, retention, and adherence to memantine will be assessed.
