Statement: Patients with measurable diseases are only eligible for phase 2 of the primary trial.
Primary_evidence: DISEASE CHARACTERISTICS:   Histologically confirmed breast cancer   Metastatic disease amenable to biopsy   Unresected tumor with no intention to undergo resection during study   Archival tissue from the primary diagnosis or fresh biopsy from metastatic cancer site required   Measurable or non-measurable disease for phase I study (The Phase I portion of this study closed and the Phase II portion of the study opened as per NCCTG Addendum 6, effective January 23, 2012.)   Measurable disease only for phase II study   Available tumor estrogen (ER), progesterone (PR), and HER2 status from metastatic site tested by IHC or FISH OR results from the original tumor diagnosis   Any ER, PR, or HER2 level (positive or negative) acceptable (phase I)   Triple-negative disease only (phase II)   ER and PR negative defined as  1% by IHC   HER2 negative   Patients with triple-negative breast cancer allowed provided there is clinical or radiographic evidence of tumor progression in the adjuvant or metastatic setting   No patients whose disease can be treated with known standard therapy that is potentially curative or definitely capable of extending life expectancy   No known CNS metastasis   Hormone-receptor status:   ER and PR positive or negative (phase I)   ER and PR negative (phase II)   PATIENT CHARACTERISTICS:   ECOG performance status 0-1 (phase I) or 0-2 (phase II)   Postmenopausal defined by 1 of the following:    60 years of age    45 years of age with last menstrual period  12 months prior and estradiol and follicle-stimulating hormone levels in postmenopausal range   Bilateral oophorectomy   Life expectancy  12 weeks   ANC  1,500/mm^3   Platelet count  100,000/mm^3   Total bilirubin normal   ALT and AST  3 times upper limit of normal (ULN) ( 5 times ULN if due to liver metastasis)   Serum creatinine  1.5 times ULN   TSH normal (thyroid hormone supplements allowed for patients with hypothyroidism)   Not pregnant or nursing   Fertile patients must use effective contraception   Willing to return to Mayo Clinic or NCCTG institution (phase II) for follow-up   Willing to provide blood samples for correlative research purposes   No uncontrolled or intercurrent illness including, but not limited to, any of the following:   Ongoing or active infection   Symptomatic congestive heart failure   Unstable angina pectoris   Cardiac arrhythmia   Psychiatric illness and/or social situations that would limit compliance with study requirements   No NYHA class III or IV cardiovascular disease   No known seizure disorder   No co-morbid systemic illnesses or other severe concurrent disease that, in the judgment of the investigator, would make the patient inappropriate for entry into this study or interfere significantly with the proper assessment of safety and toxicity of the prescribed regimens   No immunocompromised patients, including patients known to be HIV positive   Immunocompromised patients due to the use of corticosteroids allowed   No malignancy within the past 5 years except for nonmelanoma skin cancer or carcinoma in situ of the cervix   No history of myocardial infarction  6 months   No congenital long QT syndrome or QTcF>450 msec, including:   Complete left bundle block or use of a permanent cardiac pacemaker, history or presence of ventricular tachyarrhythmias, clinically significant resting bradycardia (<50 beats per minute)   Right bundle branch block + left anterior hemiblock (bifascicular block)   No congestive heart failure requiring use of maintenance therapy for life-threatening ventricular arrhythmias   PRIOR CONCURRENT THERAPY:   See Disease Characteristics   More than 4 weeks since prior chemotherapy or radiotherapy and fully recovered   No radiotherapy to > 25 % of bone marrow   Prior treatments allowed (phase II):   0 or 1 prior chemotherapy regimens for breast cancer    2 prior aromatase-inhibitor regimens (including letrozole)   Not currently receiving treatment in a different clinical study in which investigational procedures are performed or investigational therapies are administered   No other concurrent investigational agent for the primary neoplasm   No concurrent CYP3A4 inhibitors or inducers