Fulvestrant and/or Trastuzumab as First-Line Therapy in Treating Postmenopausal Women With Stage IV Breast Cancer

OBJECTIVES: Primary * Compare the overall objective response rate in postmenopausal women with estrogen receptor (ER)- and/or progesterone receptor (PR)-positive, HER2/neu-overexpressing stage IV breast cancer treated with first-line therapy comprising fulvestrant and/or trastuzumab (Herceptin®). Secondary * Compare the duration of response in patients treated with these regimens. * Compare overall survival of patients treated with these regimens. * Compare the antitumor activity of these regimens, in terms of time to disease progression, in these patients. * Compare the clinical benefit of these regimens in these patients. * Determine the safety and toxicity of these regimens in these patients. * Correlate HER2/neu expression and ER and/or PR expression with response in patients treated with these regimens. OUTLINE: This is a randomized, controlled, open-label, multicenter study. Patients are stratified according to prior adjuvant endocrine therapy (yes vs no). Patients are randomized to 1 of 3 treatment arms. * Arm I: Patients receive fulvestrant intramuscularly on days 1 and 15 of course 1 and then on day 1 only in all subsequent courses. * Arm II: Patients receive trastuzumab (Herceptin®) IV over 30-90 minutes on days 1, 8, 15, and 22. * Arm III: Patients receive fulvestrant as in arm I in combination with trastuzumab as in arm II. In all arms, courses repeat every 28 days in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed every 8 weeks. PROJECTED ACCRUAL: A total of 120 patients (40 per treatment arm) will be accrued for this study.