Fulvestrant With or Without Ganetespib in HR+ Breast Cancer

Because no one knows which of the study options is best, you will be "randomized" into one of the study groups: Arm A: Fulvestrant or Arm B: Fulvestrant plus Ganetespib. You will have a one-third chance of being placed in Arm A and a two-thirds chance of being placed in Arm B. If you are initially placed in Arm A but your disease progresses, you will have the option of receiving the combination of fulvestrant plus ganetespib as part of Arm C. You will undergo the following procedures during the research study: study drug(s), blood tests, clinical exams and scans/imaging tests.