Erlotinib and Gemcitabine in Treating Patients With Metastatic Breast Cancer Previously Treated With An Anthracycline and/or a Taxane

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed breast cancer * Clinical evidence of metastatic disease * Candidate for first- or second-line chemotherapy for metastatic disease * Must have received prior anthracycline or taxane therapy (may have had both in the neoadjuvant, adjuvant, or metastatic setting) * At least 1 measurable lesion at least 20 mm by CT scan or MRI OR at least 10 mm by spiral CT scan * The following are not considered measurable disease: * Small lesions less than 20 mm by CT scan or MRI * Bone lesions * Ascites * Pleural/pericardial effusion * Inflammatory breast disease * Lymphangitis cutis/pulmonis * Abdominal masses not confirmed and followed by imaging techniques * Cystic lesions * No active CNS metastases (treated CNS metastases stable for more than 8 weeks are allowed) * Hormone receptor status: * Not specified PATIENT CHARACTERISTICS: Age * 18 and over Sex * Male or female Menopausal status * Not specified Performance status * ECOG 0-2 Life expectancy * At least 3 months Hematopoietic * Absolute neutrophil count at least 1,500/mm\^3 * Platelet count at least 100,000/mm\^3 * Hemoglobin at least 8.5 g/dL Hepatic * Bilirubin no greater than 1.5 times upper limit of normal (ULN) * AST no greater than 3 times ULN * Alkaline phosphatase no greater than 3 times ULN Renal * Creatinine no greater than 1.5 times ULN Cardiovascular * No symptomatic congestive heart failure * No unstable angina pectoris * No cardiac arrhythmia Gastrointestinal * No inability to take oral or nasogastric medication * No requirement for IV alimentation * No active peptic ulcer disease Ophthalmic * No abnormalities of the cornea based on history (e.g., dry eye syndrome or Sjögren's syndrome) * No congenital abnormality (e.g., Fuch's dystrophy) * No abnormal slit-lamp examination using a vital dye (e.g., fluorescein or Bengal-Rose) * No abnormal corneal sensitivity test (Schirmer test or similar tear production test) Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * Sub-dermal implants and condoms are not considered acceptable forms of contraception * No other invasive non-breast malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer * No ongoing or active infection * No psychiatric illness or social situation that would preclude study compliance * No other concurrent uncontrolled illness PRIOR CONCURRENT THERAPY: Biologic therapy * At least 2 weeks since prior immunotherapy * No prior cetuximab Chemotherapy * At least 2 weeks since prior chemotherapy and recovered * No more than 1 prior chemotherapy regimen for metastatic disease * No more than 2 prior chemotherapy regimens total, including adjuvant therapy Endocrine therapy * Prior hormonal therapy allowed in metastatic and/or adjuvant setting Radiotherapy * At least 2 weeks since prior radiotherapy * No prior radiotherapy to more than 25% of bone marrow * No prior strontium chloride Sr 89 Surgery * More than 4 weeks since prior major surgery * No prior surgical procedures affecting absorption Other * No prior epidermal growth factor receptor-targeting therapies (e.g., gefitinib or EKB-569) * No concurrent combination antiretroviral therapy for HIV-positive patients * No other concurrent antitumor therapy