Inclusion Criteria:

          -  Postmenopausal women (postmenopausal: age >= 60 years, or amenorrhea >= 12 months, or
             bilateral oophorectomy, or - in women with hysterectomy only - follicle stimulating
             hormone [FSH] in the menopausal levels as per local institutional guidelines if < 60
             years old) with histologically-confirmed estrogen receptor (ER)-positive (>= 10%)
             primary breast cancer stage cT0-2, cN0-1, Mx; women with larger tumors who refuse
             chemotherapy (chemo) and/or endocrine neoadjuvant therapy can be eligible

          -  Eastern Cooperative Oncology Group (ECOG) performance status =< 1 (Karnofsky >= 70%)

          -  Leukocytes >= 3,000/microliter

          -  Absolute neutrophil count >= 1,500/microliter

          -  Platelets >= 100,000/microliter

          -  Total bilirubin =< 2 x institutional upper limit of normal (ULN)

          -  Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase
             [SGOT])/alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT])
             =< 1.5 x institutional ULN

          -  Serum creatinine =< 1.5 times institutional ULN

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

        Exclusion Criteria:

          -  Body mass index (BMI) < 18.5 Kg/m^2

          -  Previous treatment for breast cancer including chemotherapy, endocrine therapy and
             radiotherapy; women with prior ductal breast carcinoma in situ (DCIS) who were treated
             with surgery only and whose treatment ended >= 2 years prior to enrollment are
             eligible for the trial

          -  Women who are planned to receive neoadjuvant therapy

          -  Participants may not be receiving investigational agents

          -  History of allergic reactions attributed to compounds of similar chemical or biologic
             composition to exemestane

          -  Uncontrolled intercurrent illness including, but not limited to, ongoing or active
             infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac
             arrhythmia, or psychiatric illness/social situations that would limit compliance with
             study requirements

          -  Other co-existing invasive malignancies (with the exclusion of basal cell carcinoma or
             skin squamous cell carcinoma) diagnosed during the last 2 years before randomization

          -  History of severe osteoporosis (T score =< -4 either spine or hip), or presence of
             vertebral fracture

          -  Use of systemic hormone replacement therapy (HRT) in the last 30 days prior to the
             randomization; the use of non-systemic estrogen (such as vaginal estrogen use) is
             allowed

          -  Use of any chemopreventive agents (selective estrogen receptor modulators [SERM]) in
             the last 3 months

          -  Concomitant use of CYP3A4 inducer medication (rifampicin, phenytoin, carbamazepine,
             phenobarbital, and St. John's wort)