Tamoxifen Citrate or Letrozole With or Without Bevacizumab in Treating Women With Stage IIIB or Stage IV Breast Cancer

This randomized phase III trial studies tamoxifen citrate or letrozole together with bevacizumab to see how well it works compared with tamoxifen citrate or letrozole alone in treating women with stage IIIB or stage IV breast cancer. Estrogen can cause the growth of breast cancer cells. Hormone therapy using tamoxifen citrate or letrozole may fight breast cancer by blocking the use of estrogen by the tumor cells. Immunotherapy with monoclonal antibodies, such as bevacizumab, may induce changes in the body’s immune system and may interfere with the ability of tumor cells to grow and spread. It is not yet known whether giving hormone therapy is more effective with or without bevacizumab in treating advanced breast cancer.