Letrozole and Goserelin or Leuprolide in Treating Premenopausal Estrogen Receptor-Positive Patients With Stage IV Breast Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed carcinoma of the breast * Metastatic disease * Measurable disease (i.e., unidimensional by RECIST) * No rapidly progressing visceral involvement (e.g., liver or lymphangitic lung disease) * No known marrow involvement as evidenced by diffuse uptake by imaging studies or bone marrow biopsy or aspirate * No evidence of CNS metastases * Estrogen- and/or progesterone-receptor positive status confirmed in primary breast tumor or in recent biopsy of metastatic site PATIENT CHARACTERISTICS: * Female * Premenopausal\*, as defined by the following criteria: * Less than 12 months from last menstrual period or premenopausal estradiol within the past 12 months * No prior bilateral oophorectomy * 45 years old or younger with intact ovaries and not a candidate for aromatase inhibitor therapy alone due to the potential for recurrent ovarian function NOTE: \*Women are considered premenopausal after prior hysterectomy if they have intact ovaries and follicular hormone levels consistent with the institutional normal values for the premenopausal state * Women meeting premenopausal criteria prior to receiving ovarian suppression are eligible * ECOG performance status 0-2 * Life expectancy ≥ 3 months * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective nonhormonal contraception during and for 12 weeks after discontinuation of study therapy * ANC ≥ 500 cells/mm³ * Platelet count ≥ 50,000 cells/mm³ * Hematocrit ≥ 28% * In the absence of liver metastases: * AST and ALT ≤ 2.5 times upper limit of normal (ULN) * Alkaline phosphatase ≤ 2.5 times ULN * In the presence of liver metastases: * AST and ALT ≤ 5 times ULN * Alkaline phosphatase ≤ 5 times ULN * In the presence of bone metastases: * AST and ALT ≤ 10 times ULN * Alkaline phosphatase ≤ 10 times ULN * Total bilirubin ≤ 2 times ULN * No significant comorbid conditions, including any of the following: * Clinically significant cardiac disease not well controlled with medication (e.g., congestive heart failure, symptomatic coronary artery disease, or cardiac arrhythmias) * Myocardial infarction within the past 12 months * Serious concurrent infection * No lack of physical integrity of the upper gastrointestinal tract * No inability to swallow or malabsorption syndrome * No other carcinoma within the past 5 years except nonmelanoma skin cancer and treated in situ cervical cancer * No mental illness * No known hypersensitivity to luteinizing hormone-releasing hormone (LHRH), LHRH-agonist analogues, or any of the components in goserelin PRIOR CONCURRENT THERAPY: * No concurrent chemotherapy and/or additional hormonal therapy * Concurrent trastuzumab (Herceptin®) for patients with HER2 overexpression allowed