DISEASE CHARACTERISTICS:

• Pathologically confirmed invasive breast cancer with clinical, radiographic and/or pathologic evidence of stage IV disease
• Must have tissue blocks available from biopsy of at least one site of metastatic disease and/or from diagnosis of their primary breast cancer

• Disease may be measurable (by RECIST criteria) or non-measurable but must be present in at least one non-liver site and imageable on fludeoxyglucose F 18 PET scan

  • Patients with non-measurable disease by RECIST criteria, one of the following may be used to assess and follow disease

    • MUC-1 antigen level (either CA 27.29 or CEA) > 2 times upper limit of normal
    • Circulating tumor cell assay > 5
    • FDG-PET SUV > 2.5 in purely lytic lesions
    • Elevated tumor markers alone are insufficient
• Patients with disease in the liver only are not eligible

• Tumor HER2/neu expression must be determined prior to study enrollment

  • Assessment may be by fluorescence in situ hybridization (FISH) assay or by IHC
  • FISH must be performed if determination is intermediate by IHC

• Patients must be planning a course of endocrine therapy with one of the following:

  • Tamoxifen
  • Ovarian suppression using an aromatase inhibitor
  • Fulvestrant with ovarian suppression in pre-menopausal patients or fulvestrant alone
• No HER2/neu positive disease and not planning to undergo HER2-directed therapy (trastuzumab or lapatanib)
• No visceral crisis characterized by rapidly progressive hepatic or lymphangitic lung metastases

• Positive for estrogen receptor (ER) and may or may not be positive for progesterone receptor by IHC in the primary tumor and/or metastatic site

  • Pathology report for assay of ER will be reviewed by one of the investigators prior to enrollment, the study pathologist will review the pathology report if necessary for determination of study eligibility

PATIENT CHARACTERISTICS:

• Known menopausal status

  • Postmenopausal is defined as:

    • A prior documented bilateral oophorectomy
    • A history of at least 12 months without spontaneous menstrual bleeding
    • Age 60 or older with a prior hysterectomy without oophorectomy
    • Age less than 60 with a prior hysterectomy without oophorectomy (or in whom the status of the ovaries is unknown), with a documented FSH level demonstrating confirmatory elevation in the postmenopausal range for the lab
  • Premenopausal patients must have a baseline FSH, and estradiol levels to determine menopausal status
• ECOG performance status (PS) 0-2 or Karnofsky PS 60-100%
• Life expectancy >16 weeks
• ANC ≥ 1,000/mm³
• Platelet count ≥ 50,000/mm³
• Hemoglobin normal
• Creatinine ≤ 1.5 times upper limit of normal (ULN) and estimated creatinine clearance > 50 mL/min
• Bilirubin ≤ 1.5 times ULN
• AST and ALT ≤ 1.5 times ULN
• Alkaline phosphatase ≤ 2.5 times ULN
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No history of uncontrolled seizures, central nervous system disorders, or psychiatric disability judged by the investigator to be clinically significant, precluding informed consent
• No other life-threatening illness (e.g., serious, uncontrolled concurrent infection or clinically significant cardiac disease - congestive heart failure, symptomatic coronary artery disease, cardiac arrhythmia not well controlled with medication)
• Not medically unstable as judged by the patient's physician
• No psychological, familial, sociological, or geographical conditions which do not permit compliance with the study protocol
• No known allergic or hypersensitivity reactions to previously administered radiopharmaceuticals (patients with significant drug or other allergies or autoimmune diseases may be enrolled at the investigator's discretion)
• Body weight ≤ 400 lbs
• No uncontrolled diabetes mellitus, defined as fasting glucose > 200 mg/dL
• No adult patients who require monitored anesthesia for PET scanning
• No other prior malignancy is allowed except for the following: adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer, or any other cancer from which the patient has been disease-free for 5 years

PRIOR CONCURRENT THERAPY:

• Meets 1 of the following criteria:

  • No prior endocrine therapy for metastatic disease
  • Off adjuvant endocrine therapy for > 6 months
  • Single adjuvant endocrine therapy duration of > 2 years at the time of first recurrence and plan to change to alternate endocrine therapy
• More than 6-8 weeks since prior tamoxifen
• Prior chemotherapy regimens in the adjuvant or neoadjuvant setting are allowed
• Prior adjuvant luteinizing hormone-releasing hormone analog allowed
• No other concurrent investigational or commercial agents or therapies for the treatment of this disease