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 \< 55 years with a prior hysterectomy without oophorectomy or unknown status, with a documented follicle-stimulating hormone (FSH) level in postmenopausal range within 4 week s of registration, (5) receiving a gonadotropin releasing hormone analog (GnRH) to suppress ovarian function (eg, goserelin 3.6 mg every \[q\] 4 weeks) * Patients must have stage IV disease or inoperable locally advanced disease * Patients may have measurable disease only, non-measurable disease only, or both (Response Evaluation Criteria in Solid Tumors \[RECIST 1.1\]); it is anticipated that at least 50% of patients will have only non-measurable disease * Patients are required to have disease that is resistant to aromatase inhibitor (AI), which is defined either as relapse while receiving adjuvant A.I. therapy (ie, anastrazole, letrozole, or exemestane), and/or disease progression after one or more A.I.s for metastatic disease; prior exposure to more than one AI is permitted * Patient may have had prior tamoxifen but are not required to * Patients may have received up to one …