This randomized, placebo-controlled trial aims to assess the feasibility, acceptability, and preliminary efficacy of memantine and the University of Carolina (UNC)'s Get Real \& Heel cancer exercise program (MEM+EX) in addressing cancer-related cognitive impairment (CRCI) and underlying CRCI biomarkers. Ninety stage I-III breast cancer patients with mild cognitive difficulties during chemotherapy will be randomized into three groups: MEM+EX, memantine, or placebo. The study will evaluate recruitment, retention, adherence, acceptability, cognitive function, brain-derived neurotrophic factor (BDNF), inflammatory markers, and frailty at multiple time points.