Lapatinib Ditosylate and Capecitabine in Treating Patients With Stage IV Breast Cancer and Brain Metastases

DISEASE CHARACTERISTICS: * Histologically confirmed invasive breast cancer * Stage IV disease * At least 1 measurable CNS lesion ≥ 10 mm on T1-weighted gadolinium-enhanced MRI * No single brain metastasis that could be treated by surgery * HER-2 positive primary tumor as defined as IHC3+ or IHC2+ and FISH-positive * Hormone receptor status: not specified PATIENT CHARACTERISTICS: * Menopausal status not specified * Eastern Cooperative Oncology Group (ECOG) performance status 0-2 * Life expectancy ≥ 3 months * Absolute Neutrophil Count (ANC) ≥ 1,000/mm\^3 * Platelet count ≥ 100,000/mm\^3 * Hemoglobin ≥ 10g/dL * Creatinine ≥ 1.5 times upper limit of normal (ULN) * Albumin ≥ 2.5 g/dL * Serum bilirubin ≤ 1.5 times ULN (unless due to Gilbert's syndrome) * ASAT and ALAT ≤ 3 times ULN (≤ 5 times ULN with documented liver metastasis) * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception 2 weeks before, during, and for 28 days after completion of study treatment (female) or for 1 week after completion of treatment (male) * Able to swallow and retain oral medication * Affiliated to a Social Security System * No known contraindication to MRI * No prior or active malignancy, unless disease free for ≥ 10 years * No other concurrent severe and/or uncontrolled medical disease which could compromise study participation, including any of the following: * Infection * Cardiac disease (e.g., uncontrolled hypertension, congestive cardiac failure, ventricular arrhythmias, active ischemic heart disease, myocardial infarction within the past year, Left Ventricular EJection Fraction (LVEF) \> grade 2) * Current active hepatic or biliary disease (except for Gilbert syndrome, asymptomatic gallstones, liver metastasis or stable chronic liver disease per investigator assessment) * Renal disease * Active gastrointestinal (GI) tract ulceration, malabsorption syndrome, active uncontrolled ulcerative colitis, or disease significantly affecting GI function * Severely impaired lung function (e.g., spirometry and diffusion capacity of lung for carbon monoxide (DLCO) ≤ 50% of normal, and O\_2 saturation ≤ 88% at rest on room air) * No known dihydropyrimidine dehydrogenase deficiency * No significantly altered mental status prohibiting the understanding of the study, or with psychological, familial, sociological, or geographical condition potentially hampering compliance with the study protocol and follow-up schedule * Not deprived of liberty or placed under the authority of a tutor PRIOR CONCURRENT THERAPY: * At least 2 weeks since prior breast cancer treatment (e.g., trastuzumab, chemotherapy, immunotherapy or biological response modifiers, endocrine therapy, or radiotherapy) * More than 30 days since prior investigational drugs * More than 14 days since prior and no concurrent strong inhibitors or inducers of the cytochrome P450 isoenzyme 3A4 (CYP3A4) (i.e., clarithromycin, ketoconazole, itraconazole, voriconazole, ritonavir) * No prior whole brain radiotherapy (WBRT) or brain stereotactic radiotherapy * No prior treatment with capecitabine and/or lapatinib ditosylate * No prior resection of the stomach or small bowel * No concurrent systemic treatment or radiation therapy for breast cancer (except corticosteroid, bisphosphonates, or mannitol)