• Women who are postmenopausal at the start of study treatment

⁃ Postmenopausal status will be established as follows: Women who are 50 years or older and who are not menstruating for greater than 12 months will be considered postmenopausal. Women who are less than 50 years with an intact uterus and ovaries must have chemically induced menopause (e.g., ovarian suppression) to be considered postmenopausal

• Women with a diagnosis of early-stage breast cancer (stage I, II, III) treated with neo/adjuvant chemotherapy within 12 months of starting study treatment

• No evidence of active/recurrent breast cancer or other serious chronic illnesses

• Have evidence of pre-frail health, defined as a 6-minute walk distance (400-480m) at baseline

• Platelets \> 60,000/mm\^3

• White blood cell count \> 2,000/mm\^3

• Absolute neutrophil count \> 500/mm\^3

• Hemoglobin ≥ 8.0 g/dL

• Total bilirubin ≤ 3.0 X upper limit of normal (ULN)

• Aspartate aminotransferase (AST) ≤ 4.0 x ULN

• Alanine aminotransferase (ALT) ≤ 4.0 x ULN

• Estimated glomerular filtration rate (eGFR) of ≥ 30mL/min/1.73m\^2 per the Modification of Diet in Renal Disease (MDRD) calculation. GFR (mL/min/1.73 m²) = 175 × (Scr)-1.154 × (Age)-0.203 × (0.742 if female) × (1.212 if African American)

• Ability to understand and the willingness to sign a written informed consent document