Fulvestrant With or Without Bortezomib in Patients With Inoperable Locally Advanced or Metastatic Estrogen Receptor Positive Breast Cancer

Inclusion Criteria

• ELIGIBILITY CRITERIA FOR ARM A AND ARM B
• Patients must have histologically or cytologically confirmed ER+ positive breast cancer
• Patients must be postmenopausal, defined as: (1) a history of at least 12 months without spontaneous menstrual bleeding, (2) prior bilateral salpingo-oophorectomy, with or without hysterectomy, (3) age >= 55 years with a prior hysterectomy with or without oophorectomy, (4) age = 60%)
• Leukocytes >= 3,000/mcL
• Absolute neutrophil count >= 1,500/mcL
• Platelets >= 100,000/mcL
• Total bilirubin within normal institutional limits
• Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase [SGOT])/alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT]) = = 60 mL/min/1.73 m^2 for patients with creatinine levels above institutional normal
• Patients must be disease-free of prior invasive malignancies for >= 5 years with the exception of: curatively-treated basal cell or squamous cell carcinoma of the skin, carcinoma in situ of the cervix
• Patients must have the ability to understand and the willingness to sign a written informed consent document
• Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation; should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately
• ELIGIBILITY CRITERIA FOR ARM C
• Previously met all eligibility criteria for arms A and B and registered on trial to arm A (fulvestrant alone)
• Disease progression on arm A and agreeable to crossover to arm C
• Has received no intervening therapy (ie, alternative endocrine therapy, chemotherapy, biologic therapy) between disease progression on arm A and registration an arm C
• ECOG performance status 0-2
• Tumor measurements (eg, computed tomography [CT] scan of chest/abdomen/pelvis) within 4 weeks of registration to arm C
• Leukocytes >= 3, 000/mcL, within 2 weeks of registration on arm C
• Absolute neutrophil count >= 1, 500/mcL, within 2 weeks of registration on arm C
• Platelets >= 100, 000/mcL, within 2 weeks of registration on arm C
• Total bilirubin within normal institutional limits, within 2 weeks of registration on arm C
• AST(SGOT)/ALT(SGPT) = = 60 mL/min/1.73 m^2 for patients with creatinine levels above institutional normal, within 2 weeks of registration on arm C

Exclusion Criteria

• EXCLUSION CRITERIA FOR ARM A AND ARM B
• Patients who have had chemotherapy or radiotherapy within 4 weeks (6 weeks for nitrosoureas or mitomycin C) prior to entering the study or those who have not recovered from adverse events due to agents administered more than 4 weeks earlier
• Patients may not be receiving any other investigational agents
• Patients with known brain metastases should be excluded from this clinical trial
• Presence of rapidly progressive, life-threatening metastases; this includes patients with extensive hepatic involvement (> 50% of the liver involved), symptomatic lymphangitic metastases, or brain or leptomeningeal involvement
• History of allergic reactions attributed to compounds of similar chemical or biologic composition to bortezomib or fulvestrant
• Patients who are concomitantly receiving bortezomib and drugs that are inhibitors or inducers of cytochrome P450 3A4 should be closely monitored for either toxicities or reduced efficacy
• 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
• Human immunodeficiency virus (HIV)-positive patients on combination antiretroviral therapy are ineligible
• Patients who have previously received fulvestrant
• Patients who have previously received bortezomib
• Concomitant antic