Gefitinib in Treating Patients With Metastatic Breast Cancer That Has Progressed After Antiestrogen and Nonsteroidal Aromatase Inhibitor Therapy

DISEASE CHARACTERISTICS: * Histologically confirmed breast cancer * Radiological and/or clinical evidence of metastatic disease * Progressive disease after prior therapy with an antiestrogen (e.g., tamoxifen or faslodex) and a nonsteroidal aromatase inhibitor (e.g., anastrozole or letrozole) in the adjuvant and/or metastatic setting\* NOTE: \*Endocrine therapy must be the last treatment before study entry * Unidimensionally measurable disease * No rapidly progressive visceral metastases * No uncontrolled CNS metastases * Hormone receptor status: * Estrogen receptor and/or progesterone receptor positive PATIENT CHARACTERISTICS: Age * 18 and over Sex * Not specified Menopausal status * Postmenopausal, defined as any of the following: * Natural menopause with at least 1 year since last menses * Radiation-induced oophorectomy with last menses more than 1 year ago * Chemotherapy-induced menopause with 1 year since last menses and serum follicle-stimulating hormone, luteinizing hormone, and plasma estradiol levels in the postmenopausal range * Surgical castration Performance status * ECOG 0-2 Life expectancy * Not specified Hematopoietic * Not specified Hepatic * Bilirubin no greater than 1.5 times upper limit of normal (ULN) * Transaminases no greater than 2.5 times ULN * No severe or uncontrolled hepatic disease Renal * No severe or uncontrolled renal disease Cardiovascular * No severe or uncontrolled cardiac disease Pulmonary * No severe or uncontrolled respiratory disease * No evidence of clinically active interstitial lung disease * Asymptomatic chronic stable radiographic changes allowed Other * No other malignancy within the past 5 years except adequately treated carcinoma in situ of the cervix, contralateral breast cancer, or nonmelanoma skin cancer * No psychological, familial, sociological, or geographical condition that would preclude study compliance and follow-up * No other severe or uncontrolled systemic disease * No known hypersensitivity to any excipients of gefitinib * No unresolved chronic toxicity greater than grade 2 PRIOR CONCURRENT THERAPY: Biologic therapy * No concurrent biologic agents Chemotherapy * No more than 1 prior chemotherapy regimen for metastatic breast cancer * No concurrent chemotherapy Endocrine therapy * See Disease Characteristics * No concurrent hormonal therapy Radiotherapy * Prior radiotherapy allowed * No concurrent radiotherapy to any metastatic site Surgery * No surgery within 4 days after study drug administration Other * No prior epidermal growth factor receptor inhibitor therapy * More than 30 days since prior investigational drugs * No concurrent use of any of the following: * Phenytoin * Carbamazepine * Rifampin * Phenobarbital * Hypericum perforatum (St. John's Wort) * No concurrent systemic retinoids * No other concurrent investigational drugs or treatments * No other concurrent anticancer treatments * Concurrent bisphosphonates for the treatment and prevention of bony metastases are allowed provided therapy was initiated before study enrollment\* NOTE: \*Bisphosphonates may be initiated during study participation for the treatment of hypercalcemia only