Exemestane in Treating Postmenopausal Women With Stage IV Breast Cancer

Inclusion Criteria:

Histologically or cytologically confirmed metastatic carcinoma of the breast
Hormone receptor (estrogen receptor [ER] and/or progesterone receptor [PR]) positive disease (defined as: ER and/or PR positivity as >= 5% staining), as confirmed by immunohistochemistry (IHC) based on primary breast tissue or metastatic tissue
Postmenopausal, as defined by any of the following:
Natural menopause, with at least 1 year since last menses
Chemotherapy-induced menopause with at least 1 year from last menses and serum luteinizing hormone (LH)/follicle-stimulating hormone (FSH) and estradiol levels within the postmenopausal range
History of surgical or radiation-induced ovarian ablation
For women =< 56 years old and with a history of hysterectomy but at least one ovary intact, serum LH/FSH and estradiol levels must be within the postmenopausal range
Postmenopausal women with disease recurrence while receiving either tamoxifen or a non-steroidal aromatase inhibitor (AI) as adjuvant therapy (as long as adjuvant hormonal therapy was taken for 6 months before disease progression) or with disease recurrence following the discontinuation/completion of adjuvant hormonal therapy
Postmenopausal women with disease progression following either 0, 1 or 2 prior hormonal therapies for metastatic breast cancer, as long as the subject has had no prior exposure to exemestane (EXE)
Measurable or non-measurable (but evaluable) disease, as defined by RECIST criteria
Eastern Cooperative Oncology Group (ECOG) performance status of 0-1
Neutrophil count >= 1.5 X 10^9 cells/L
Platelet count >= 100 X 10^9 cells/L
Serum creatinine =< 1.5 times upper limit of normal (ULN)
Total serum bilirubin =< 1.5 times ULN
Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) levels =< 2.5 x ULN in patients without liver metastases or =< 5 times ULN in patients with liver metastases
Alkaline phosphatase =< 2.5 times the ULN for patients without bone or liver metastases
Subjects must have an estimated life expectancy of greater than 6 months

Exclusion Criteria:

Prior exposure to EXE, whether in the adjuvant or metastatic setting
Prior history of any other cancer with the exception of non-melanoma skin cancer and treated in situ carcinoma of the cervix
Active or symptomatic central nervous system (CNS) metastasis (stable or treated brain metastasis allowed but patients must be off decadron, if given for CNS disease)
Hormone-receptor negative or unknown breast cancer
More than two prior chemotherapy regimen for treatment of metastatic disease (any prior chemotherapy given in the adjuvant setting is permitted)
Administration of any other anti-cancer therapy within 2 weeks of initiating study treatment; use of bisphosphonates, however, are permitted for patients with known bone metastases
Treatment with any other concurrent investigational agent or anti-tumor drug (chemotherapy, antibody therapy or other biologic agents), will not be permitted
Subjects who have had no prior exposure to endocrine therapy
Any uncontrolled medical co-morbidity or psychiatric disorder which interferes with the ability to provide informed consent or comply with study procedures