Chemotherapy and Hormone Therapy as First-Line Therapy in Treating Postmenopausal Women With Metastatic or Locally Advanced Breast Cancer

OBJECTIVES: * Determine the optimal sequence of chemotherapy and endocrine therapy as first-line therapy in postmenopausal women with metastatic or locally advanced breast cancer that is potentially sensitive to both modalities. OUTLINE: This is an open-label, randomized, crossover, multicenter study. Patients are stratified according to participating center. Patients are randomized to 1 of 2 treatment arms. * Arm I (chemotherapy first): Beginning within 4 weeks after randomization, patients receive chemotherapy\* comprising either an anthracycline- or a taxane-based regimen, or a combination of both drugs, according to local institutional guidelines. Treatment continues for 6 months or longer, in the absence of disease progression or unacceptable toxicity. After discontinuation of chemotherapy, patients receive endocrine therapy comprising oral letrozole once daily in the absence of disease progression or unacceptable toxicity. Patients with immediately life-threatening disease (e.g., lymphangitis carcinomatosa or liver involvement exceeding 1/3 of the liver) are recommended for second-line chemotherapy. NOTE: \*Patients may receive chemotherapy on a separate clinical chemotherapy trial but must first undergo randomization in this study. * Arm II (endocrine therapy first):Beginning immediately after randomization, patients receive oral letrozole once daily in the absence of disease progression or unacceptable toxicity. Patients who demonstrate progressive disease then receive chemotherapy as in arm I. Quality of life and pain are assessed at baseline and then periodically for 5 years. After completion of study therapy, patients are followed periodically. PROJECTED ACCRUAL: A total of 1,500 patients will be accrued for this study.