Patients and healthy volunteers undergo cognitive function testing consisting of neuropsychological battery tests and complete self-reported questionnaires (e.g., Squire Memory Self-Rating Questionnaire, and FACT-B Quality of Life Measure) regarding cognitive ability, quality of life, fatigue, and psychosocial status. Patients and healthy volunteers also undergo geriatric assessment at baseline and after 6 months of initiation with aromatase inhibitor therapy.